This is the exact same reason why I didn't play either, the really crappy optimization for my mac. That and I have a controller now. If you can get a controller for it, definitely go for it! Feels way better to play with it then a keyboard.
I actually ended up switching to controller because using WASD/^<v> was inflaming one of the muscles in my hand really badly. Inflamed hand muscles are not so good for playing double bass, so I plugged in my controller, and ended up being REALLY happy with how it controls. I ended up having to play around with how all the ephemera was set up (buttons for bombs, pills, "spacebar" items, map button) a little bit, but now i'm at a place where I suck, but at least I can't complain about it being the control scheme's fault!