The Advantium 120 convection oven function (that uses a conventional heating element and a fan) is actually the same as the 240. The microwave in the 240 is slightly more powerful but similar. The major difference is with the speedcook mode that uses halogen lights along with microwaves to cook, allowing the A240 to cook almost as fast as a microwave but retaining most of the cripsier texture usually only possible with a standard oven. The 240v version, besides being twice the voltage, is also twice the amperage (30 amps instead of 15), so it has access to up to 7200 watts instead of only 1800. As GE points out, this allows the speedcooking on the 240 to be twice as fast as the 120. What GE doesn't make clear is that the A120 also relies much more on microwaves to cook than the A240 does (check the published specs for the differences, noting the halogen lamps are much higher wattage in the 240). So food speedcooked in the A120, besides taking twice as long to cook, have a bit more of that soggy microwaved texture, although it can still cook noticeably better than a microwave for many foods. So basically if you want the Advantium mostly for the conventional cooking mode and/or as a microwave oven, the A120 works fine and about as good as the A240; but for the speedcook mode the A240 is substantially faster and cooks better. Correct that only the 120v Advantium is rated for installation under a countertop, and only the 30" wide version, not the 27". I think some other brands (Miele? Electrolux? Jenn-Air?) allow installation under a countertop with their 240v speed ovens; check the installation instructions. There's also the Advantium 240v over-the-cooktop model, which works very well in all cooking modes, though the oven isn't as deep front-to-back as the wall-oven versions and the exhaust fan isn't as powerful as a good separate range hood.

We also have a 120V advantium (ours is OTR) and really like it. The newer ones seem even better than ours, but ours works just fine. We use it more for microwaving and regular baking (rather than speedcooking) but we do use the speedcooking capability from time to time. From what I understand, the new ones have a rack that can go in which I really like the idea of - my one caveat to ours is that it has only the turntable, on which you need to fit your baking dishes - not always the easiest size to fit. We did have problems with the bulb about a year into owning it, but we didn't bother replacing it at that time. It had a big circuit board problem though about 2 months ago which was pretty expensive to fix - that said, from what I understand our experience was atypical (and may have been a power surge issue). In addition, there is an online site (I think it was instuctables.com) that explains how to replace the bulb yourself. Bottom line? We're doing an addition to our new house and completely redoing the kitchen, and I'm pretty positive there will be a 120V Advantium (possibly the Monogram this time) in that kitchen (along with a 36" gas range and a Gagg combi-steam). We find its flexibility extremely useful.

I had a 120. I ended up using it mostly as a microwave because anything you put in has to be fairly small, and cookware must be non-metal and round, since it has to rotate on the turntable. For feeding a family of 4, it just wasn't that practical. I did occasionally use it to heat up Dino-nuggets and the like. Otherwise, it didn't get much use in speedcook mode. We just finished a remodel on our new house and I decided against the Advantium and went with a warming drawer instead. I have to say I LOVE IT. I use the warming drawer almost everyday. Favorite appliance so far, even though I do like my induction cooktop, there is a learning curve. The warming drawer is simplicity.

The wall-oven Advantium definitely suffices as a second oven. By and large, so does the OTR version - when used as a convection oven, you can insert the shelf and get extra capacity (IIRC the turntable can be shut off to so you can use the full width of the lower shelf of the oven). When used as a speedcooker, it's fast enough (especially the 240v version, which I recommend) to cook several dishes one after another in the same time you could only cook one item in a conventional 2nd oven. The Advantium can do warming-drawer duty as well. The speed cooking mode works especially well with rolls and bread-wrapped items. If you can go with 24"w or 60cm (23") cooktop and separate oven, you may buy the countertop space you need. Some of these narrower cooktops give you as much cooking space as typical 30"w range - this is done by using very small knobs at the front, sometimes all four are offset to the right so the left two burners can use the full depth of the cooktop, front to back. These often allow a drawer to be placed directly below them for convenient cooking utensil storage. The turntable in the built-in Advantiums is 16" round. Don't have the dimension for the OTRs, think it's around 13". There are alot of imaginative layout options that solve insufficient space problems - i.e. I've used undercounder freezers, sometimes the drawer type, paired with a 30" or 30"w separate all-refrigerator rather than a 36"w side-by-side fridge/freezer to buy an extra 6" of countertop space,, and the aforementioned separate 23"w cooktop and undercounter 24"w oven to buy another 8" of countertop space (see my May 22 post in this thread).