I had a 560Ti for 3 months and sold mine for a loss of $30. I didn't mind cuz I used it for a couple months. I sold it to a friend and it had warranty still.
If you are doubting and wanting more, then upgrade. I splurged to a 660Ti. Mind you I went from 560ti to 660ti. I love the boost, but it depends on what you want to get out of your GPU. At 1080p it plays what I want at great speeds and quality. If you bought a 660ti you'd be impressed.
The 660ti price is high. I completely agree with people that say it should be lower, like $270 or so. It could drop in price, but if your willing to spend $300-320, then consider a 7950.