Upload & Sell: Off
This Spring, I bought a T3i as a backup for my 40D & add-on for my daughter since her 10D died.
I like the Rebel well enough, and I love the IQ and image size, but I hate: the size, feels tiny; controls, too different from my 40D; slow FPS, I find it too slow for my 300 F4 on birds, etc., and also too slow for bugs with my 100 F2.8 non-IS.
I do like the articulating screen, when it's handy, it's very handy.
I like carrying both, T3i with flash brkt and macro, 40D with the 300. The Reb is light enough to always bring with, unless it's too hot or I'm already too gear-heavy.
I wanted another 40D as our new body, but video tipped the balance for her. No complaints with the T3i, nice camera, but for macro & wildlife, which are my everyday interests, I like the 40D better. For walk-around, portraits and not-everyday-carry, she loves the T3i.
If I could do it over, I'd get the 40D, especially since I use the Reb more than she does.
Just my thoughts.
Someone else made the point about the 5D batteries: T3i batteries and SD cards are different then 40D batteries and CF cards. Also, the T3i battery only lasts about 400-500 shots for me, sometimes less, while my 40D goes 600-1000 depending.