TheMadScientist - 10:45 pm on May 9, 2011 (gmt 0)
I have one I launched the end of Feb that's ranking fine, but it seems to be 'the exception' rather than 'the rule' ... I would guess some of it's 'niche specific' and some is site & link dependent ... I'm actually surprised it ranked as well as it did 'out of the gate', but not complaining either.
My guess would be walkman is correct about the 'lack of level of trust' in most niches, so it's probably a waiting game coupled with some consistency and stability on the site and wrt inbound links.
ADDED: My guess is user behavior when it gets 'that hour in the spotlight' probably has something to do with it too.