...and in five years you'll be just like the people today that are running Windows 98, or Windows NT.
It's wise to keep up to date with your OS and productivity software. Vista SP1 is almost officially out, and that's the signal for me that Vista is ready. I use the SP1 rule with just about any software.
If you are in charge of deploying the OS, as well as being responsible for a flood of support calls, take your time. Are YOU ready to support Vista? Is your support team ready?
The main gripes with Vista are UAC and user rights. If you don't have a plan for this, stay away from a Vista deployment. Personally, I turn UAC off, and remove administrator rights from a non-administer user. Drivers used to be a common problem, but Vista has been out long enough where any respectable company has supplied Vista drivers. Make sure that any "Must have" applications are Vista ready...some older ones are not. Test them first.
Finally, make sure YOU have plenty Vista experience. I have been using Vista since beta2 and have had no problems to speak of that I haven't noted above.
Also, I would recommend that Vista is deployed to a limited number of users as a trial. Pick users that are tech inclined, and users that have new machines. Don't try to install Vista on machines that are several years old. An easy way to do this is to introduce Vista on new workstations as the are installed, or replaced.
You know what I mean. Take your time, understand it, have a plan, and everything will go smooth. IMHO, Vista is ready (@SP1) for deployment, and I say this truthfully, not as a geek that is just defending all that is new.
Good luck,
Paul