That's up to their own owners of course.
I know SleePy set up a cronjob to synchronize his (live-but-not-public) test site.
Kindred updated his last night (or the day before).
I don't know all the others.
If you only tested the alpha you have missed many fixes for sure.
If you downloaded the tarball of the release-2.1 branch in the last week then you have tested everything, but not a couple or two features that will (hopefully) go into 2.1 as soon as they are ready.
