well, the gt330m dgpu in my mid-2010 mbp is causing gpu-related kernel crashes. but, i don't think it is about heat, if that is what you're worried about.
if the gt650m hasn't had gpu-related crashes then i don't think it will suffer the same fate as the gt330m. the gt330m from the get-go has always had gpu-related issues. it was about intel igpu to nvidia dgpu graphics switching and now in mavericks, it is not about it switching so much anymore but a gpu-related kernel panic crash about read error and apple mux control or something like that which could be the same grafx switching issue before that causes the KP even though it is not switching anything if that makes sense....
this is my theory but it could be how OS X and certain programs inherently or sneakily will use the dGPU for "cpu" task but to my mid-2010 MBP--the task that the OS uses to ask the cpu or dgpu to leverage task in the OS might be tripping over the old switching graphics thing that causes it to KP. idk how to make it mroe clear, just a theory and i am not an engineer.
as for overheating like the hd6550m's in the 2011 mbp's? the 650m is by nvidia and i think it's kepler based so the 650m should be thermally sounder than what AMD usually offers for the same performance. so, the 650m might not fry itself like the hd6550m.
fry itself is the operative word. i am hoping that the 650m is smarter than that and since apple is still using it's faster sibling, the 750m in the highest priced rMBP, then apple probably doesn't see a problem with it.
although, it's hard to tell if apple sees anything since they apparently didn't see the GT330m's "latent manufacturing defect" or that the HD6550m would fry itself inside their aluminum clad computers.