If you're a developer of multiple projects like me, you'll find yourself needing to switch between multiple different Version Control Systems (VCSs). After I've worked on one project using, say, SVN for an hour I may need to switch to a different one that's using, say, git. That's where I start beating my head on a wall.
Not because I dislike either system; I actually like both of those. It's because my mind thinks "check that in" and then my fingers have already started typing "svn commit ..." instead of using "git". It's just habit. The VCS should be getting out of my way, but because there are so many it just got in my way. I can't work on auto-pilot because different projects need different VCSes.
# cd svn_repository_checkout
# or update
# or diff
# or commit -m "woot"
# cd cvs_repository_checkout
# or update
# or diff
# or commit -m "woot"
# cd git_repository_checkout
# or update
# or diff
# or commit -m "woot"
# cd svk_repository_checkout
# or update
# or diff
# or commit -m "woot"