I have the 40D (still have it) and upgraded mine to 7D because
- Main reason: The 40D had problem so I need to get a replacement. I believe it maybe related to the mirror mechanism or the shutter itself (Err99). It will still take photos, but occasionally, it gave Err99 with I press the shutter button. And I need to pull the battery out to reset it.
- I like a camera that can take video with my fast lens as well.
- I like a camera that has more than 9 AF points
- For what I shoot, full frame may not be a perfect format for me. (If I shoot weddings or portraits most of the time, then FF maybe better for me)
- Do not want to spend too much money.
- Do not want to sell my lenses (I can, but I do not think my photos are going to be better if I change, so why bother)
Hence, I pick up the 7D.
However, if my 40D still works perfectly, I do not think I will get the 7D at all now.