Well I'm in that exact situation. Most workstations I have are Win95 (with some NT4.0 and Unix for CAD). I recently spent ~$18,000 in XP licenses for all machines. W2K and XP licensing were the same price. I will actually install W2K though.
Some reasons:
* program compatability is known/tested in more cases with W2K than XP. From the business stand point this is very important because some program vendors will not support a configuration with XP clients. Others vendors have relatively limited support knowledge.
* system stability is still more certain with W2K
* many OS exploits are well known (and patched) with W2K now
* W2K seems to do better with the same resources that are common in my enviroment (per informal testing)
On the other hand some XP only features sound good:
* rewritten/improved kernel (more stability?)
* seemingly better restore/repair methods built in
* built in remote desktop feature seems promising (but potential security problem?)
* ability to use an IRC server to make use of the built in "instant support option" (at least from I've been told)
* better multi-lingual OS support built in
I sent an associate to a WinXP support class in late Dec. (I forget the MS class number). His opinion was that W2K & XP do very similar things as far as our working enviroment goes.
So, no compelling reason to go to XP with so many unknowns and the lack of support for our applications.