If you use MacVim and are lucky enough to own a MacBook Pro with a Retina display, then you may have noticed performance issues. Users are reporting slow scrolling and unexpected latency when entering text.
Fortunately, enabling "experimental rendering" appears to fix the problem. This can be found in the Preferences, Advanced menu (
Björn Winckler responded to say that he can't test this because he doesn't have a machine with a Retina display, which is understandable, but just goes to show how difficult testing a popular product can be even on Apple's hardware (given the smaller variance in hardware compared to the PC as a whole).