[xwiki-users] meaning of "milestone 1" of XE 3.0?

Hi - I see that XWiki Enterprise 3.0 Milestone 1 was just released a week ago. I also found the roadmap at http://enterprise.xwiki.org/xwiki/bin/view/Main/Roadmap I can't tell from the announcement however what the intended use is... Is this something that is likely to blow up ("alpha" quality)? At what point in the roadmap does it make sense for a new install to try a 3.0.x release instead of 2.x release? In addition to stability of the software, what about stability of any APIs - are those frozen in M1? If I adopt M1, will M2 automatically upgrade from M1, or are automatic upgrades only assured for migration from a stable 2.x release? When 3.0 final is out, will work on 2.7 basically stop? Will the current release of XWord work with XE 3.0M1? Regarding extensions, the listing at http://extensions.xwiki.org/xwiki/bin/view/Main/ says nothing about version compatibility. I'm guessing that because of the velocity upgrade, trying any extension with heavy velocity usage would be a gamble with XE 3.0M1 ? Or is there an automatic "smoke test" report somewhere of what extensions are certain to not work? Sorry for all the questions, but I seem to have hit xwiki at a cusp in its lifecycle so I'm in a quandary about which version to start with. -mda