@Chip Bennett - Nice idea for sure. I don't think we'd need to actually introduce a new value for that. Running a development version is enough to receive auto-updates to that branch. Unfortunately, that means you automatically "skip" to the next branch (so you'd go directly from 3.7-RC2-golden to 3.8-alpha). I actually prefer that, because it means people continue to test trunk, rather than us losing our body of testers each release. What actually should happen is the beta tester plugin should give you a proper choice: Do you want to just test 3.7, or do you always want to be on the bleeding edge? This is something we intend to revisit in 3.8.