Hello,
I found myself thinking about the same upgrade some 2 months ago. The 50D is by no means a bad camera, but you might want to read this:
http://www.dpreview.com/reviews/canoneos50d/page31.asp
You will find similar advice and conclusions elsewhere.
In the end I chose the 40D, not the 50D.
happy shooting anyways! posted in 50d and 400d