I think that a missing factor in making this decision is the shape of an automatic test suite. Its been mentioned a dozen times and has the potential to tip the scales in favor of the time-based releases (making QA easier -> shorter freezes). In the event that we are able to maintain QA (by test suite or other) then +1 for time based releases. Its very convenient for users to know when releases will be and makes following software much easier as a whole.
For those who don't mind the cutting edge though, I don't see a problem with still keeping minor revisions every other week with major revisions every 6 months, e.g: 1.x.y, incrementing y every 2 weeks incrementing x every 6 months
-Zach