I installed the daily build of Ubuntu 15.04 tonight, as I wanted to test the beta of the latest AMD proprietary driver which is currently only available for 15.04. Borderlands 2 finally runs with 60fps, everything maxed out on my 290x. I doubt I'm the first to notice the performance improvement, but since I didn't see anybody else mentioning it, I decided to share. Please, bear in mind it's still not as good as in Windows - there are annoying frame drops which I hope they'll fix by the time of the final release. And while I'll definitely continue playing it in Windows, I can wholeheartedly recommend Linux purists who had the same problem to give it a try. It is finally in a state in which you can actually enjoy it.