So many times so far Ive read reviews of games like boarderlands and bioshock and whatnot not working on macbooks and imacs they clearly should work on given the Specs, if this helps out even one person Ill be glad, try this, go into your system perefrences > Universal Access > ENABLE ACCESS FOR ASSISTED DEVICES!!!! click on that last one so that its check marked and then try your game again, and I bet you anything it works great! I remember when I first got steam on my mac, I got portal, super simple game my macbook could BARELY handle it on lowest settings, I had all the same problems all the reviews are saying on the app store, then I did alittle looking into the FAQs on steam and BAM, found out about that assisted devices button, EVERY game I have from steam now runs on full specs, and they look and act fantastic!