It's not easy, is it? Imagine being able to spool up a new environment (on one server as opposed to, say, 5 in production) and feed it a copy of production data, run tests, and then tear it down. And imagine knowing that this environment was identical to production in every way except for minor configuration changes to get it to run on one box. And when you're done with it? Throw it away. That's really powerful. A new employee comes on board? Here, here's your environment. Mess with it as much as you want, we can just rebuild it if you totally hose it. All QA except for performance testing, which would need to be done on real hardware anyway, could be done in these environments.