[citation][nom]UpsetCanonFollower[/nom]Sadly they used the *same* sensor as the T2i, T3i cameras, with a slight adaptation for the improved video focusing. Nikon and the rest must be high-fiving, since it seems Canon cannot come up with a better APS-C sensor than the old 18mp one. I just bought a T2i for a good price when the stats for the T4i were released...[/citation]
Sadly? Have you really even used your T2i? The T2i produces fantastic images, the sensor is very good and 18MP is plenty. At 25MB for each RAW file, i'm not sure i want any higher MP. Remember this is still an entry DSLR.
TH doesn't go in depth on how the AF system is improved. The largest improvement really is through video. Not sure if you've tried to use autofocus while using liveview/video, but it's just terrible. This new autofocus system allows for much faster and accurate focusing during video.
I'm strongly considering ditching my T2i for the T4i.