H.264 data rate for 550D?
 

What is the approx. data rate upon capture for this camera?

QuickTime Player reports data rate of aprox 48mbits/s for 1920x1080 29.97 footage.

Is anyone editing the footage natively? Or, are you transcoding to another format?

Transcode for best results.

I have to transcode with the 5D and assume this is the same on the T2i, but perhaps your computer is faster. I use Apple ProRes and final cut, and on my version of Compressor, the "Apple ProRes" default setting was actually making ProRes HD clips, which were super huge and unnecessary, FYI. A friend of mine claims ProRes Draft quality is so good no one will notice the difference, which might be true if your final destination is the web- I can't say for sure.