Running on a rMBP, early 2013, 16gb ram and SSD, 2.7ghz, i7 - I have no issues with it running all medium, havent tried any other level yet.
Also running on my iMac mid 2011 with 8gb ram, all medium settings, very smooth on both systems.
I have disabled vsync on the rMBP as I don't believe it's need for the retina display.