There are plans afoot to designate Mozilla Milestone 12 as the Alpha version of the browser. The criteria for alpha are:

1. Quality: Mean Time Between Failures should be at least 1 hour. The MTBF for the M11 release was 1.09 hours according to talkback reports

2. Architecture: Alpha should be "almost architecturally complete". "Almost" is a recognition that there will be some exceptions; it's not an excuse for large design holes. "Architecturally complete" means that all public XPIDL interfaces have been reviewed for correctness, completeness and aesthetics; and have then been blessed by mozilla.org.

3. Acceptance: There's a consensus in the Mozilla community that M12 is usable. Ideally, a majority of M12 users will try to live in Mozilla as their primary browser and mail program, ane restart it when it crashes. We don't want to set an unrealistic goal just yet, but we will measure and poll after M12 is out, in order to decide whether it was in fact "usable".

Milestone 12 is due out in the middle of December.