When I used one in Lion is was just, not sorted, just felt stuttery all around. Though I understand ML helped that a lot. I primarily use my 13 especially when traveling just b/c I prefer its size vs the 15, and will pry replace with the new 13" rMPB. I haven't really seen many post talking about how the 15 rMBP handles virtualization? I run OS/X and Win7 parallel sometimes, and since we all know the new tax the OS has now on ram as well as pushing that screen etc, has anybody used it with Parallels/Fusion/VirtualBox running Win7 simultaneously??