writes "Microsoft is imploring millions of Windows 7 beta testers to perform a clean install of the forthcoming Release Candidate, rather than upgrade from the beta. 'The reality is that upgrading from one pre-release build to another is not a scenario we want to focus on because it is not something real-world customers will experience,' the company claims on the Engineering Windows 7 blog. Those who attempt to install the Release Candidate over the beta will find their path blocked."
I've read complaints that reviews of new Linux distros often focus too much on the installation process; Microsoft seems to understand that complications at installation time (dual booting? preserving an existing data partition?) can sour one's experience pretty thoroughly.