One nice thing about the current XT rear derailleur is the low normal option (i.e. "rapid rise" where the thumb shifts up just like the front derailleur.) I was tentative about this system, but when I recently had to get a new derailleur, I decided to try an XT low normal (760) and I found that I really like it. It felt very strange at first (which is why I believe a lot of people don't like it), but it only took one ride to acclimate to it, and I find that it actually feels more "natural" to have both shifters work the same way (i.e. finger shifts down, thumb shifts up.) So far, it shifts quite smoothly (better than my previous LX rear) and has given me no problems. I'm using it with the regular Deore rapid fire shifters.
I know what you mean about seeing a lot praise for SRAM shifters/derailleurs on these forums. At the same time, however, I've been using Shimano for a while and I've had none of the problems that SRAM users complain about in regards to Shimano derailleurs -- they work smoothly and in my experience they don't need "constant adjustment" like some SRAM users have said. I have XT front and rear with Deore shifters, and they work great with no fuss. At this point, I would personally go with the XT gear, and I'd recommend the low normal rear derailleur.
Regarding the cassette, I'm currently using a SRAM cassette with an XT 760 rear derailleur (and Shimano chain) and it works fine. Many bikes come from the factory with Shimano derailleurs and SRAM cassettes.
Larry