because i've only just upgraded, and cloning a fresh VM & installing CS6 was quicker than installing it, then removing it when weird things happen (mostly plugins/file compatibility have pained me in the past).

And sure there are lighter ways to test different browsers, but I don't trust them, been caught out before by silly differences like font rendering, testing eflyers outlook express/outlook etc, in the multi-ie-in-one-app things before, now i have a one-keystroke switch between an environment i can trust 100% to be authentic, and is easy to move around too.

basically using vm's in this way is one of the things that let me sleep at night.