Spent the whole day on the CVS to Subversion migration for one of our projects. Wound up with the mime-types screwed up, then somehow got the repository into a state where it was impossible to merge between a branch and the trunk because the resulting merged file would always be out-of-date.

Eventually just decided to abandon the project history and work from a fresh export/import, but that's a solid 5 hours of work to do what should have been a few minute's task. Argh.