I am glad retina Mac guests are finally supported in v. 12. However, the performance leaves a lot to be desired. I followed all the official steps to optimize performance, and it only resulted in a marginal improvement. It is not unusable, but compared to my Win 8 guest it's sluggish. Frame rates are also dropping regularly. I am on a 2015 rMBP with 16 RAM. So I'm not on a sluggish machine.
