And to add to the above, what (if anything) are you finding limiting with the 40D ?
If its a case of you just fancy a newer model and upgrade, then what's your budget and what would you like the new body t,o do - full frame (5D) or very fast fps (7D) or just a newer model with a few extra features and a lower price tag (60D) ...
There's nothing wrong with just fancying an upgrade, I'd personally try to explore the features I like / am having issues with on the 40D and improve on these with the new body - eg the 60D is not a magnesium body that the 40D is so if you were after a lighter body, then it's the ideal choice or not if you like the weight of the 40D