So far a mixed bag with the EVGA 660ti on a gigabyte GA-Z77X-UP5 TH.
The good:
Boots fine with dual monitors (1 DVI, 1 HDMI).
Shows up as proper card in About this Mac
Cuda is active and (mostly) useable
The bad:
Premiere Pro CS6 doesn't see as usable/accelerated by Mercury Engine without editing the opencl_supported_cards.txt file
FCPX does not like this card. Applying any effect will result in a checkered screen and a locked OS X. Have to reboot to get back
Diablo III lags and stutters badly at max out settings
Can't get 3 monitors going with DVI + DVI + HDMI. It either both the DVI connections or a DVI and a HDMI.
Getting a Display Port cable tomorrow for my Asus Displayport monitor connection to see if that works for a third display.
Trying some tweaks to see if I can get it to work.
Also make sure that you DON'T have Graphics Enabler = Yes. You won't see a screen if you do. Let the Mac handle the card without injectors.
-Alex-