In a managed environment like an office with even a half competent admin, you really don't need the additional security "features" of Vista. Unlike a lot of techies I can see what they are trying to do, and why it's a good thing when the computer is put in the hands of numpties, even though I hate it personally.
In many ways it's exactly the same as cars. I'd imagine the majority of people here to be enthisiasts who prefer RWD, no ABS, possibly no PAS. Theres also going to be a few loonballs who actually like double declutching (these people would run DOS or OS/2

) but in the hands of the numpty behind you on the motorway who is tailgating you, you will be much happier if their car has ABS! And FWD is safer in the hands of a numpty even if it does have performance disadvantages.
The only real difference is they haven't (yet) found a way to force you to upgrade your car in order to make it compatable with modern roads.
If you don't beleive this analogy has any merit, think on this: Vista sounds a little bit like Vectra
Also, you realise that Microsoft licences come with downgrade rights? Your XP licences can be used to run MS DOS or Windows 95 if you like, so providing you keep your XP CDs around there is no reason not to get Vista licences, then install XP. Of course it helps if you have a corporate key for your organisation.