I went from the T2i to the 70D. I was after the video focusing abilities and higher fps for stills. I also expected some noticeable improvement in high iso performance because of the newer sensor, upgraded software, etc.
2 out of 3 isn't bad, I suppose. The video focusing and stills frame rate are sweet. The buffer fills fast at perhaps 12 RAW images, but its far better than the T2i at 3-4. As far as IQ goes, I don't notice a difference- certainly not enough to justify the upgrade. But for improved function, the upgrade was a win.