We are working on performance improvements and I’m sure that with time it’ll get much better.
For now you can try this quick patch for non-Intel graphics cards: http://cdn.unrealengine.com/qfe/QFE-FromCL-2027741-Shelve-2030638.zip? Just unzip and run the installer.
Also, try hiding the Unreal Engine Launcher. On some Macs it helps with the performance (we will have a proper fix for this soon). And in case of Retina MacBook Pros, it appears that if you have your display mode set to higher than Best (Retina) the editor performance may suffer considerably.