I used to do this ...
I used to do web programming and I setup a virtual machine for my development environment ... it took so long to configure everything the way I wanted it and to get the server playing nice with the debugger and all that ... plus managing snapshots was a lot faster than making and restoring backup images.
My actual PC was constantly chaning .. XP to Vista to XP, new motherboard, memory, processor upgrades, install/uninstall of games, drivers software ... but my work environment was always the same even if I was on a laptop or another computer entirely.
That had its advantages and was well worth the performance hit.
Anyway I can see how attractive this would be in a corporate environment ... just as long as they don't try to implement it on underpowered machines.