I suggest we should move to Hadoop 0.20.203.0 for the next release. (Not 0.21 or further.) It is a much more recent branch of 0.20.x and is compile-time compatible with 0.20.2 in our code already.
However I know already that switching to it causes some failures, in the Lanczos jobs for instances. Looks like something's expecting a file somewhere that isn't where it used to be. I bet it's an easy fix, but don't know what it is yet.