I tried the usual recipe to reverse-merge an unintended commit:
svn merge -rBAD_REV:BAD_REV-1 .
and was perturbed to get, as a response, merely a message about mergeinfo. No actual revert of file content to the previous rev.
I went and did the fix up in another tree where I could use svn 1.6.x, but I ended up wondering: was it doing the right thing and not telling me, or has the recipe changed?