I'm sure this discussion may be buried somewhere in the forums, but when I was still debating whether or not I should shell out the 60 dollar entry fee I had a hard time finding answers. Still not knowing if I was able to get decent performance, I went ahead and spent the cash. Here are the specs of my MacBook Pro-
MacBook Pro (Retina, 15-inch, Mid 2015)
Processor: 2.2 GHz Intel Core i7
Memory: 16 GB 1600 MHz DDR3
Graphics: Intel Iris Pro 1536 MB
I'm also running the latest version of El Captain
I'm here to let you know that I'm able to run on the Ultra preset without any lag or choppiness at 1440 x 900 resolution.
There is one minor issues I have run into, which is minor screen tearing. If you don't mind this kinda thing, it is not bad enough to effect your gameplay. Personally, I find it annoying. Solution: Vsync. This does lock you into 30 fps, but this doesn't bother me any. Smooth Sailing.
So there you have it, if the only thing keeping you on the fence is not knowing whether or not your Mac can handle it, don't fret. Newer Mac's can handle gaming a lot more than people give them credit for.