I’ve been using VMs for browser testing since the ’90s when Connectix still owned Virtual PC. Recently, Chris Morris introduced me to Microsoft’s own Modern.ie project. It’s an effort to help developers test against IE’s rendering issues, and a big part of that comes by way of provided pre-built VMs for common host platforms. The VMs are time limited, though, and so every so often you have to reinstall from a VM snapshot or the original download image. Not a bad price to pay for such handy tools.