I'd say that's a fair point. One bad Beta can mess up a lot of the installs that follow it, particularly with development tools that don't uninstall the Betas properly!
As a software house, almost all of our company's internal testing is on Virtual Machines now. Increasingly the Beta's go on those too, although when it comes to dev' tools I can't help but try them on "real" hardware. Hmmmm....I wonder if that VS2008Beta will perform better with the corporate McAffee config.