I had a stoneware pie pan...unglazed Pampered Chef. I bought it used and ditched it after using it once. Fat from pie crusts had leached into the stoneware and gave a rancid flavor to the crust. Conclusion was that unglazed stoneware is a bad idea.

I love glazed stoneware for lasagna. I have a modest and a big Bunzlauer (Polish), and a pair of giant white ones with handles for feeding the dozens. Whether stoneware or foil or something in between, I always bake lasagna at 350° F for 45 min., or 50 for the giant ones. Loose foil on top if it starts getting too brown.

I've used my mother's little one for vegetables, and that was very nice too. Mine are too tall for that, though I've made vegetable casseroles in them.

I also have an unglazed stoneware deep dish pizza pan. I've only used it a couple of times, and it still isn't as well seasoned as I'd like, but it's great. It does stain, of course.

My daily bread is baked in a seasoned but unglazed terracotta banneton. I like how it comes out so well, I was given similar loaf and baguette pans, but haven't had a chance to do more than season those.

To season unglazed stoneware or terracotta, use a not smelly oil with a high smoke point, like safflower or sunflower (the banneton was done initially with peanut and it still smells peanuty). Here are the Mason Cash instructions for the rest: http://www.masoncash.co.uk/how-to-season-a-terracotta-bread-form  I find at least three times works better.

With unglazed, you should oil it every time you use it as well.

OTOH, as far as I'm concerned, clear glass is the only thing for pie. In a pinch, I'll use white Corning, and it works fine, but the clear Pyrex is superior. I have a ceramic tart pan that was a gift, and very pretty. It's fine for quiche, and would be okay for a cookie crust tart, but not proper pie dough.

Pink, you're right that they're heavy--I have a hip high, side opening oven, so probably don't notice it as much. I use OXO big mitts with the silicone ridges that keep the pan from slipping, and protects my forearms. And I have a strong back and shoulders. Perhaps put some heavy cans in yours and practice lifting it in and out of a cold oven. You might find that once you expect the weight of it, it's fine. If not, and you want to do the oven to table, get a pretty shiny steel lasagna pan and let it look like what it is. No one will care that it's "industrial chic" if they're getting homemade lasagna. :)

I use my unglazed rectangular baker for scalloped potatoes. A friend served lasagna in hers and it had turned a lovely dark patina from usage and was very well-seasoned. It wasn't light coloured at all any more.

These are glazed pans.

I have an oval Le Creuset dish (glazed) I use for things like scalloped potatoes or casserole type dishes. Prefer aluminum baking sheets for roasting veggies.

With glazed, ignore everything I posted about seasoning. :)

As I said, I love my deep stoneware dishes for lasagna and other casseroles. Also bread pudding.

So, re the veggies, steel is a conductor, though a poor one compared to aluminum or copper. Ceramic is an insulator and it compares better to glass. It makes sense that your veggies take longer, and if the dish is heavier empty, it's going to be heavier full. One thing I like about stoneware for veg--especially well spaced out--is that it is a more gentle cook. It's also fairly non-stick. I usually only cook veg in raw steel if they're being steamed, or cooking with a chicken or something, though I will roast hardier veg that I also want to dry out on an enamelled steel baking tray, usually with parchment paper to control sticking and make cleaning easier.

So, that's a long way of saying, yes, your veggies are going to cook differently in stoneware, but you may find reasons to like it. But if you just don't like dealing with the weight of it, you can always just use it as a desk accessory. :)

Someone 'earthy' was blogging about stoneware for cooking a while ago. Admitting it was given free to test. I like the idea and have a few, one for a bread loaf i was given as a gift. Well seasoned now but we do bread other ways more successful.

I seldom give to a thrift for some things i may re-visit. Happens often.

Research and see if it needs seasoning as mine need. Just might become a favorite for a few dishes.

Last night I made meatloaf in a stoneware casserole dish and it took TWICE as long to cook (2 hrs. instead of one). Dinner was a half hour late and I ended up cutting off the ends and frying them just so we could eat finally. I am swearing off of stoneware, it does not fit my lifestyle! It might be OK for bread but not going to work for anything else for me.

I love stoneware for cooking things. I don't notice a longer cooking time for anything.

Wow! Yes, it obviously isn't working for you, so your choice is wise, but it seems so odd to me that it would take so much longer! I bake muffins in a Polish pottery (stoneware) muffin pan, and it might take a minute or two longer than the aluminum, but not a significant time.

Yeah, seems weird to me too. I dunno, I think I am going to have to check my oven. I use stoneware for bread, and I think it is fine for smaller things.

I prefer stone ware....I do have one large stainless baking pan....but much prefer the stone ware. Stainless gets hot and burns stuff at the edges rather than baking evenly. If you are finding vast differences in cookign times, there is something else going on there. Can't happen! Might make a difference in bottom browning...or burning, but not in general cooking time. oven cooking doesn't come from the pan but from the oven temp. As a science teacher you should know that.
As you said....check the oven...but keep the stoneware!

It's true that there is some insulation effect, but there also is, if not as much, with glass and pyroceram. Corningware is supposedly made of the stuff they created to cover space ship nose cones and protect them from the heat of friction with the atmosphere, or something like that. Steel is a conductor, but a relatively poor one.

There shouldn't be more than a 10 minute, at the outside, difference in cook times for a lasagna in any of them, and likely less to none.

Checking the oven is a great idea.

Though...since stoneware works fine for bread and smaller things, it's potentially a preheating problem.

Pink, how long do you preheat your oven for? It's well known that when the air at the sensor is at the correct temperature for the pre-heat signal to go off, the entirety of the oven, the walls, etc., often isn't completely hot. This is true with convection ovens as well, though not as dramatically since the convection speeds the heating time. I can see how with the mass of a big lasagna and the insulating effect that Ci_lantro pointed out, the stoneware might take relatively longer in an oven that had just barely come to heat.

If you wanted to give it one last try, heat the oven for at least an hour, and set the stoneware dish by a sunny window in the morning, or put it somewhere else warm to come up to at least room temperature before building the lasagna, it might make a difference.

Check the weight of a stone ware dish, vs a corning wear dish....that should tell you there is not a lot of air in stoneware.
EVERY TIME I get better results baking a pie in a stoneware dish versus a corning or a glass...or an aluminum pan, don't have a stainless pie pan>
I also have baked rolls and biscuits and cookies on an aluminum cookie sheet and a stainless one and directly on a baking stone in the oven. The baking stone gives the best results hands down....the stainless one burns the edges and top before the center is done, because of the weight factor on that large piece of stoneware, I usually use aluminum.
Ask a pro like Martha Stewart, or Julia Child or Alton Brown what material is best for baking.....hands down it won't be stainless.
Check your oven....stoneware is as good as it gets!

Perhaps my stoneware is cheap. I don't like stainless either. I use aluminum for cookie trays, lined in parchment. Best cookies. I have never had a pie crust turn out cooked on the bottom with my stoneware pie plate and I haven't had good luck with pre-baking in it either. The one kind of cookware I do like is cast iron and enameled cast iron. I have a bit of graniteware, I might try a few more of those. I have mostly Pyrex type baking dishes, they are serviceable and what I use most often. I figured stoneware would be a lot like them. Has not been my experience.

Interesting that in this comparison article, the testers noticed a slower cooking time with ceramic. Food and Wine, best baking dishes

Even if it is, that wouldn't make such a big difference.

Since you like glass, why not just stick with it?

Amazon has a nice glass lasagna sized dish from Anchor Hocking.

I have the glass Pyrex/Anchor Hocking type stuff, which I am going to stick with, and a selection of steel stuff. Am pruning my stuff to fit into my new house, while absorbing my mom's stuff. Short on space, the stoneware is going. It looks nice but just doesn't fit my cooking style. If I want slow, even cooking I have cast iron for that. I kept the stoneware bread pans, and one high end ceramic roasting pan that was mom's.

Enamel ware is just steel with an enamel coating....notably poor for cooking, but cheap. Popular with the people who couldn't afford tin lined copper and didn't want to deal with cast iron.
Recipes tell you to lower oven temp by 25 degrees when using glass, or shorten cooking time....
And remember that both glass and stoneware hold heat lots longer then stainless ( which shouldn't rust!)....so while your food is "cooling" it's also continuing to cook.

Oh! Pruning. Well, then, why not use the big stoneware dish as a mail tray or something? Because it's pretty.

I've researched it and used my experience. All cookware has its pros and cons and best application. I can live without stoneware for cooking. My pies, casseroles and lasagna turn out fine on my other pans. Someone else will love my cast offs.