My wife and I bought a used one in '08 and got a chance to really experience the TT this summer while we were down in Pagosa Springs. My wife lived in it for about 5 months while helping out some friends and I spent about 1 week out of each of those months in it. We have a 2000 M-18 (19' x 7' 6") with the 2 drop down beds on each end and I think we both agreed that it was a little tight, even for just the two of us. Now granted, most people wouldn't be living out of it for months at a time and as for previous camping trips we made, it worked out just fine. It's when you start living out of it and start carrying t.v.'s, vcr's, and all the supplies, clothes, coats, and whatever else you might need is when things start to get a little tight. I think that we would be happier with the 21ss model, but then that would change my winter storage situation and I don't really want to pay someone to let it sit on their property for the winter. I like the idea of parking it on the side of my garage and covering it up for the winter and if we buy something new for it, we just step outside and open her up and add it in.
The 21SS model that i mentioned has the two bunk ends that drop down, just like ours, but the off-door side has a super slideout (SS) that pushes a couch and a dining area out and opens up the floor space between the kitchen and these sitting areas. Talk about leg room! Anyway, that would be a perk to having the 21 over the smaller 18. I believe they also make a 21 with just a couch slideout and with 3 drop down bunks as well, but I don't know those models off hand. i think they also make a 23 footer in this SS setup as well.
Showering in a camper is a first time perk for us, but an even newer experience on how to deal with the short life of the 5 gallon hot water tank. We learned how to conserve water in a hurry, that's for sure. No more daydreaming while soaking in the steam like we did at home.
I do have an appreciation for the push button ignition within the camper vs having to go fire off a pilot light outside. Do yourself the big favor and no matter what you get, make sure that hot water heater has the electric heating element along with the option for propane heating as well. Electric is great for the misc. warm water needs and the propane makes it nice for fast recovery for those early morning showers.
One thing that really bugged me about this camper was the stock sized tires and rims that came on it. Long story short, I replace the 13" wheels and tires for a 14" and have been very pleased since the day I did this. I have a write up in here somewhere about getting some help from the fellas and getting it done shortly there after. So, assuming that they install those 13" wheels and tires on the new ones, if you get the opportunity to upgrade the wheels and tires on it to a 14", do it! You'll save yourself a LOT of headaches later.
One thing that I really enjoy on ours is the full slide through storage bin in the front section of our Roo. I store everything in there from axes and camp shovels to the dog bowls and the fold up chairs. It's really nice to not have to unpack that stuff every time we clean out the camper. I don't remember if they are still including that slide bin area up front, but I would miss it and it would be a deal breaker on my next purchase if it didn't have something similar to that on it.
Another upgrade I did in ours was in the shower. Not sure why they did this (other then to save money) but our shower didn't have the vinyl or plastic shower wall surround it in. I saw an add for a 2002 model for sale, same M-18 model and it didn't have the shower walls in it either, so I thought this might be worth the mention. The walls that were in there were the same material as you would find in the hallways, that taped and textured type stuff. So, I bought the acrylic surround from a guy near work and installed it over the existing walls and it's worked out really well for us. No leaks or issues during that entire 5 month stay (knock on wood).
I'll leave it at that for now, but if you have any other specific questions about our experiences, feel free to let me know. I'll be happy to share our experiences with you.