We are now synced to the latest revision of Box2D on google code, r57.
We had a couple of bugs which we have recently ironed out, so there are no known issues. We will play around with it for a few days and then if no new issues appear update the recommended release to this revision.
We did notice a slight perf hit with this latest revision but it is not well understood what regressed. We have an issue to track that down and reclaim the 10% hit on Pyramid test.