There's been no activity on the atomic-revprop branch on the last few weeks. I haven't had time yet to work on the ra_dav error chain marshalling (via the 207 XML parsers in ra_serf/ra_neon). Once that's done (presumably on trunk), the final svnsync patch can be applied and the branch merged.
I'll work on it again when I have more spare time and less $work deadlines. Sorry. Daniel