With Resolve 8.2.2 on Lion with the rMBP I get an error that the 650M is not supported and that CUDA isn't working. However, performance still exceeds that of the same software configuration on my 2011 17" MBP. I have to be careful though and make sure I have the computer set to use the Nvidia GPU. Even with auto switching turned off sometimes it doesn't seem to change so I use the gfxCardStatus utility (http://codykrieger.com/gfxCardStatus) to force it to the Nvidia. I also restart the computer and don't run anything else other than Resolve in order to be sure I avoid the out of GPU memory error that sometimes shows up if I run something else.
Also, I tested Resolve 8.2.2 on Mountain Lion GM and it was a no go on the rMBP. I get a few different errors related to the GPU. The CUDA driver that installs with Resolve is an older version than what's current and won't update through the preferences panel. I downloaded the latest from Nvidia website and that installed but didn't fix the problem. I also found the 5.0 CUDA driver beta and that didn't fix it either. When I try to load a project/session in Resolve it completely crashes out every time. 8.2.2 is supposed to be Mountain Lion compatible so it appears to be a Resolve/650m compatibility issue right now. However, note that my rMBP is defective and this could be related to that, but I'm guessing not since the rMBP is not officially supported by BMD for Resolve right now.