The one point I’d disagree with, though, is your assertion that “realistically, the average user only downloads and installs official test releases.” I’m pretty sure that even the average user doesn’t really run test releases — because most people don’t have the luxury of potentially screwing up their system, whether it’s for a test release or for rawhide.
Which is one of the things that makes the new USB stuff so awesome. The process for building a bootable USB key running rawhide is basically trivial at this point, and the biggest risk for most people of running rawhide — blowing up their one stable, working machine — becomes a non-issue. Plug in the key. Run your system. If something is crazy broken, unplug it, reboot to your stable box, and file a bug. If we play our cards right, this could *dramatically* increase the number of people who are willing to run rawhide — or even our test releases.
My $0.02: we really need to resurrect Fedora Bug Days — and it might be really useful to make Live USB the core enabling technology behind this effort.