Vista is being beta tested as we speak and the roll out of that product will NOT be bug free, can we afford to wait when there is a working version of Win out there now? Don't forget, many companies will not jump on the Vista bandwagon until after 6 mos to a year just so that others can shake down the bugs and fixes and the product is stable before they convert. I've worked in Info Tech for over 30 years and the last 13 years on windows based operating systems, I for one would not recommend or put my company at risk just so that I can say that I have the latest Microsoft operating system. A running business cannot afford the risk rewards of an operating system upgrade especially on both ends (client and servers).
Many companies will take the conservative approach when it comes to operating system upgrades, as their current software will be supported at least 12 to 24 months after the new software that replaces it us generally available.