When you start talking about a clean install on a machine that is not your dev environment, the words “continuous integration” come to mind. If you can automate some QA, then that's better than nothing, and having something automatically check out new builds and install them fresh somewhere other than your dev environment, that can catch a lot of bugs. “Works on my machine” is not a valid response to a bug by a developer. What if you forgot to add a file to a repo (something I do on occasion) — testing it on your box expose the problem that your users will face.

Ralph Meijer recently pointed me to buildbot for continuous integration and I may try it out.