The best you can with 600D (550D/60D) is: (limited by hardware SD transfer rates)
- 960х540, upscale it to 1280х720 (24 fps max)
- 1280х400, tight aspect 3.20:1 (24 fps max)
In Canon's 720p - lineskipping 1.66х, so you should upscale to restore correct ratio:
- 1280x400 upscales to 1280x664 - near to 16:9 (24 fps max)
- 1280x360 upscale to 1280x600 - 2.13:1 aspect
- 1280x320 upscale to 1280x533 - 2.40:1 cinemascope aspect
It is only 1280px wide, but pretty nice looking though 
Really can't complain with that. With it being RAW detail should be amazing. Better than the h.264 codec. Not to mention cinemascope is where it's at

I haven't been able to test it out. How is framing done? Does it change in liveview mode so you can frame properly or does it require cropbar overlays?