There are no horrible stories: I've been using Xcode 3.1.2 with SVN for almost a year now, and that's good enough. Xcode SCM (version control manager) is pretty simple but stable. The only thing that fails is to delete the file.
When you delete a file, Xcode will also suggest deleting the file from version control, but when it comes time to commit it, it will complain that the file is missing. Therefore, I usually do "svn rm" from the terminal to delete the file, rather than deleting it from the Xcode Files and Groups panel. If I forget and svn continues to fuss, "svn cleanup" usually sorts it.
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