You know, I don't recall having any problems with my X-Fi XtremeGamer card under Vista, and I installed most of the stuff off the CD; I didn't notice much (if any) difference from how the card worked on XP. In all honesty, though, I haven't really used the various apps in Vista, and mainly just use the Creative control console/Creative volume panel for my day to day stuff, but I never noticed any problems. Music sounds great in Entertainment Mode, and games sound great in Game mode (Crysis and Fear ftw!

).
Creative's support is comprised of morons (I saw this last week when I had a strange problem with my X-Fi card's Entertainment mode in XP). They continually misdiagnosed the problem. I ended up fixing it myself somehow...it was broken in XP and worked in Vista perfectly. I reformatted Vista to fix an issue where SP1 would not install, and the next time I booted back into XP, it worked!?
Still, Creative sounds like they're in the wrong here. nVidia hasn't forced RivaTuner to shut down, or stop production of all the modded drivers made for GeForce cards, as well they shouldn't. These type of things are generally only used by people who know what they're doing anyways. Creative should take a page from nVidia's book (or even ATI's for that matter; they haven't tried to stop it all either).
The real problem is, of course, is my X-Fi card is the best sound card I've ever had; I don't even *know* of any alternatives that are worthy of my near-audiophile ears. Not within the price-range I paid anyways... lol