I use AS perl for developing in-house software. I do most of software development on XP, but some on Win7. Rollout from XP to 7 is usually not a problem.

Performance is reasonably good. So far, the only major thing that can be a pain in the seating device is working with the registry on 64 bit systems. You really have to always keep in mind if your program is 64 or 23 bit (they don't share registry that well).

If your programs need administrative rights, you may have to adapt your software, because just running under an administrative account may not be enough. You may start your journey here. Or, if you can, just disable that UAC thingie. Most malware bypasses this without problem anyway.