Another surprising omission for the world's best IDE.
And what's even more annoying is that Eclipse does this, and does it very well!
When using SVN, there is no 'at-a-glance' way to tell which branch you are currently using. It's not shown in the project viewer or the status bar.
You can find it by looking at 'subversion working copies information' and pressing 'refresh', but that strikes me as an extra step that shouldn't be needed (and do remember to press the 'refresh' button or you may end up committing to the wrong branch).
This request has been hanging around in one form or another for quite some time (71738, 92966, 97347,100022...)so I think it's about time Jetbrains showed it some love and fixed it