Having contracted for msft for a few years I can tell you what you should already expect - it varies.

There are the fanatics that insist on using vista and live search instead of google because anything else would be "helping our competitors".

There are the normal xp/vista + VS people, I would wager most people fall into this category.

Then there are the awesome crazy ones, the people who write the .net CLR and windows drivers and stuff seem to use VS, source insight or emacs.

There are also macs around, but very few. There are a lot of tablet PCs, I think msft itself is the worlds largest consumer of those things.