After many years (OK, decades, but who's counting?) when I finally got a dedicated room again I set up a 7.1 system using Mirage smaller speakers (OMD-5 fronts, OMD-whatever center, Omnisat v2 surrounds and backs). It was pretty cool, but at that time there were like, maybe, three 7.1 discs around and two I didn't care to buy. It seemed lacking a bit, and too often the derived rear channels just did not seem to add much. I switched in my bigger Infinities (Alpha or Beta, forget) L/C/R and the sound improved, but the surround experience didn't really, and I went back to 5.1.
A year or two later I made some major changes, getting out my old Magnepan's (MG-IIIa) and adding a Maggie center to replace the Infinity mains (which moved back to the upstairs family room system). I also switched from a Sony to a Pioneer Elite and decided to try 7.1 again since I had the speakers sitting around. There were more 7.1 discs out and the new Pioneer's surround experience was much improved. I ultimately dumped the little Mirage sat's for a full set of Magnepans (MC-1s) and have not looked back. As others have said, on some material it is just sort of nice to have, but on other material that really uses the 7 channels it is amazing.
There are pix of my room in the Magnepan thread. The room is fairly small, 13' 3" wide, 17' 7" long, about 8' 6" high, and heavily treated. It is also acoustically isolated from the rest of the house. technically, it is 7.0, since my subs are stereo in parallel with my L/R speakers (via an active crossover).
FWIWFM - Don