I have never been in one - I imagine they are a lot like small hot tubs? I think that would be fun in a master suite
I have a large jetted tub, and I love it. I use it often in the winter when it's really cold out - a long, hot soak with jets on part of the time feels wonderful. I also like it when I have a part of me that's especially sore (feet from wearing high heels, or neck and back from sitting in front of the computer). I can turn the jets so they hit those spots specifically and act like a mini-massage.
They are harder to clean than regular tubs because you also have to make sure you clean the jets themselves. But not much harder.
My guy and I like to go in there together sometimes, too.
If you've never been a bath person, though, it might not be worth the extra money.
Finally, if you get a large tub, remember that you will need a LOT of hot water to fill it, so make sure your water heater is large enough for that. When I first moved into my condo, I couldn't figure out why it had a 50 gallon water heater since my place is only 2 bedrooms...once I filled the tub the first time, I realized why.