My reference to it not being enough is when you go beyond 4xAA. Which has been shown on Toms when they did their review of the 660Ti. Once when you go to 1080p and with beyond 4xAA it falls with out an overclock.
Edit: I know also that new drivers came out for both camps and both cards have seen big improvements. the 12.11 beta drivers for AMD are very good and boosted my fps in battlefield by 20 fps on my 7950. Not sure if its the same boost that the 7870 got though.
Technically the GTX660Ti is supposed to be compared to the 7950, not a 7870, however the 7950 after overclocks and the 12.11 Drivers absolutely stomps the GTX660Ti in terms of raw speed, not to mention it's higher memory bandwidth bus and more memory. However the GTX660Ti is obviously superior to a 7870, I'd get the 660Ti just because of the extra technologies that come with it, and extra raw speed is always a plus, plus considering you're most likely spending 1000+ dollars anyway, whats an extra 40?
I did a lot of research on the current AMD 78XX cards, and finally bought one (HIS Turbo 7850) several days ago. I would strongly suggest you go with the nVida card...or a different 78XX. This Sapphire card is on clearance for a good reason.
Other Thoughts: Whoever said that if you have an SKU higher than 11199-03 you shouldn't have issues is incorrect. I have an SKU of 11199-19 and the card has serious problems. Probably won't buy from Sapphire again."
I remember back then when i mention about the gtx 660ti i damn near got my head chopped off now its a good card..My opinion as the few months ive had it yes the memory bandwidth/memory bus could be higher yes but for the card it is its not to shabby and gets the job done and will hold you over untill your next upgrade.