well, I wouldn't really call TS lenses "new" - the Canon ones have been out for a while (I use Canon exclusively so I don't know about other brands).
I think TS lenses are a lot less limited in use than a Fisheye since they can also be used as primes.
If you happen to be near a Canon workshop of some sort try to attend because you will be able to try them out as well as all other lenses that are too expensive for normal pockets.
The main characteristic of a TS lens is that it reduces or eliminates distortion due to the size of the subject and the proximity of the camera. Because of that historically their main use has been in architectural photography, but landscape photography use is becoming more and more popular.
TS lenses are truly different from regular lenses and you will know that as you as you put your hands on one since it does take a while to learn how to use it and quite a bit o master it, but the results are amazing.
I had posted this before but I'll post it again since I took it with the Canon TS-45: