Over on Signal to Noise there's a discussion of the speed with which writeboard fixed the obvious blunder of not locking documents.
The obvious discussion gets started: Was this held back to have some good news to offer real fast, or is this really a rapid release cycle. Some think so, some dismiss that as rampant conspiracy theory. It's impossible to tell of course, but it's worthwhile to mention that Jason Fried suggested doing exactly that (holding back features) as a marketing strategy in his talk at Reboot. Of course he didn't suggest that you should tell people another story in public. Personally I'm not sure I like the suggestion either way.
Also: The whole "no public betas" discussion seems like religion over fact to me. In both schools (i.e. Google vs. 37Signals) products get releases with plenty of flaws and shortcomings. In both cases your best bet is to hope that they're working hard to improve the product. As far as I'm concerned I derive no comfort from having the beta sticker removed when I still have to expect bugs and feature changes/additions as a part of life with the product.