Well, I'm using TortoiseSVN at work, in conjunction with AnkhSVN - plugin for Visual Studio 2003. Don't ask me why, I do NOT like SVN in first place but this is what old projects use in the company I work in. And lately I had to do some changes in old project, so installed TortoiseSVN 1.4.x and AnkhSVN 1.0.2. This worked just fine for a couple of months but today I have decided to upgrade Tortoise to latest version.
Yes, blame me, I forgot that this is an Open Source project and they do NOT think about backward compatibility. Never. Guess what? Guys in TortoiseSVN decided to change format of their "working copy" and Ankh has stopped working because it doesn't know about the new format. Mind you, I have upgraded from version 1.4.x to version 1.5. Not from 3.0 to 10.0 and not even from 1.0 to 2.0. Damn, I wasn't suspecting such ignorance even from open source community.
Oh and BTW, there is no Ankh client for VS 2003 that can work with new format. So I'm in process of backing up projects, uninstalling new version and installing version 1.4.x instead.