Using virtual machines for testing software is great. I can try out anything I want, and there’s never any risk of trashing my main dev machine (which avoids hours of lost coding time!).
I’ve been using virtual machines since the 1990′s, and frankly I couldn’t develop without them. (I’ve also got a lot of experience running a private cloud of VMs for one of the UK’s fastest-growing tech companies, but that’s a topic for another day or maybe a conversation over a nice whisky at one of the upcoming conferences ;)