Well...you have the traditional jetted tub, we often think Jacuzzi brand, which have a pretty vigorous set of jets and fairly strong water circulation. On the plus side they have more vigorous jets, downside is they can be noisy, and the plumbing in the older designs held water after the tub was drained. If soaps or oils are used in these tub, the water/oil in the plumbing can sometimes mildew out and turn gunky.

Newer versions of jetted tub are closer to being self-draining so they don't hold water. But there still may be restrictions on bath oils, fatty soaps, etc.

At the other end (sort of) are the air tubs. Think along the lines of the Bain brand of tubs. They have perforations in the tub shell that air is pumped through. Sort of like a bubble bath. They have a little bit of water agitation, but it's not nearly as vigorous as the jetted tubs. It's more of an all-over bubbling versus the spot massage you can get with a true jet. Less noisy. No water retained in the workings of the tub, so there aren't the same restrictions regarding bath oils that you might find with the jetted tubs.

In between? Think Sanijet. They advertise it as a "pipeless hydrotherapy tub" or something similar. Each "jet" is sort of a self-contained port. The port takes water out of the tub, turns it 180-degrees, and injects it back into the tub. Not as vigorous as a true jetted tub, but more than the air tubs. Quiet, pipeless, and the jets pop right out of the tub for cleaning when and if needed. Easy to do.

A spa I did some work for installed several of the Sanijet tubs. Nice quality build, quiet, they seemed pretty good.

Kohler has a pretty comprehensive line, if you visit their website or a Kohler showroom you might be able to get a good idea as to which tub will best provide for your needs.

I recommend finding a showroom where you can sit in the tub to "try it on".

Some tubs are better insulated than others, some have built-in heaters. The piped tubs like Jacuzzi heat the water. The air tubs like Bain inject heated air.

There are in-line heaters that can be added to jetted tubs, the heaters run about $250 plus installation. I don't believe Sanijet has a heater, but they are well insulated. I forget what they advertised, something like they only lose 2 or 3 degrees over 30 minutes.

If an air tub (like Bain) doesn't provide the vigor that you're looking for, then check out Sanijet and a jetted tub. Compare noise, ease of cleaning, and vigor of the jets.

The Sanijet did have a pretty nifty set of controls. Different massage patterns, etc. A little more customizable than Jacuzzi or Bain.

It's a wide open field to a certain extent. Comfort and ergonomics is a huge part of the soaking experience.

Overall I think Sanijet has the better product considering low noise and good water action.

All these tubs come in "drop in" versions so they can be installed in a platform.

Well, browsing around the Kohler site will help. Tubs get quite expensive fast, for the hydrotherapy etc., but there are some affordable options. Faucetdirect.com is a great place to see a variety of makers' things too, but I think Kohler is more informative as to types. Also American Standard's site.

You'll see what are called air baths, too, worth reading up on, not sure exactly of the difference between those and other spa-type tubs.

You'll need to decide between cast iron, Americast (American Standard's some-sort-of-metal-covered-with-a-coating) and various levels of quality of acrylic).

You'll need to see where your tub fits ... is it in a 3-wall alcove so one side of the tub will be visible, or will it be the kind you need to tile in? (Lots of other things too.)

A standard size is 5' by 30" or a little wider ... but with spa tubs they often vary in size beyond that.

You may want to measure how deep the inside of a tub you know and love is, and also the height from the bottom to the overflow valve. Those are two measurements you'll see that will help you distinguish too-shallow tubs from suitable candidates.

Some people like big tubs. I like deep ones but I don't like wide ones. Years ago I was at a B&B that had a terrific slanted back (sort of a great lumbar support, you could lean back and relax). I *think* there's a chance some of American Standard's tubs are like this. But - I really like the solidity of cast iron, such as Kohler.

Anyway, the Kohler site is a great place to start and explore. Don't let the prices scare you - they'll be better at FaucetDirect.com.

Also along with the many things you'll need to decide re tubs, will be left hand drain and faucet, or right hand, or middle. (For instance, think about where the drain is now if your existing tub or some other you've seen in a house is in a 3-wall alcove.)

Thanks so much! You guys are full of great information. I will jump right in and look at sanijet and kohler and american standard.

I have a jetted tub and really love it. It doesn't have heaters, but stays warm and I just add hotter water towards the end of my soaking to keep it comfy. I have a surround to sit on which is very handy. I know you will love your tub, it is so relaxing and helps with stiff joints.

I really like the sanijet 710. It looks deep and warm, and I'm all about easy cleaning. I'm just hoping that posted price (about $5,000) isn't final.

I'm in the DC metro area, but I can't find where to see/hear/lay in it. Any ideas?

And does anybody know what happened with the lawsuit? I would think if Sanijet's claims were without merit, then the big companies would have crushed Sanijet. So there must be something behind the marketing.