I'm at about 125 machines currently, most of which are members of the domain. I just took over beginning of this year, and the network is a total disaster, and I wouldn't dream of abusing it like that lol. Part of my problem is I have a lot of specialized application machines (like asphalt plant control computers) that I can't touch or won't because I'm not sure on the compatibility. One of my plants has a total POS control system in it that I know would go ballistic if I even thought about W7.
I'm currently working on upgrading the WAN links, and my top most priority project is a total infrastructure upgrade. Probably going the Dell route with a 3-2-1V solution running vS and an equalogic array. It's my first true dive into virtualization, so I'm nervous but not afraid.
WS8 seems like they're addressing a lot of their issues to match what VMWare offers, but who knows, Microsoft says they're gonna do a lot of things they never actually deploy. Right now, the only advantage of HyperV (for someone who hasn't touched either) seems like licensing costs.