should I upgrade?
If I would have a 40D already, I would opt for the 60D - for sure!
There are lots of features the old style xxD series never had (Video, display) that come with that camera - so why buy a clone of the 40D with some new (and nice) upgrades?
I should mention that I personally have the 50D and am happy. It is not so much a question of quality. It is a question of features.