I was a happy Canon 40D owner.
I was surprised to hear about a replacement after only 12 months and I started collecting information about the new model: 50D announements promised 50% higher sensor resolution, four times the predecessor’s sensitivity and a VGA display aligned to the best competitors (and further add-on functionalities that filled – partially – the 40D’s gap wrt competitors).
Despite I had no reason to change, I decided to upgrade to the new model that I coupled with my excellent and well proven Canon 24 – 105 L and Sigma 18-50 lenses.
First shots, first disappointments: soft images, “flat”, with several examples of misfocusing.
After 300 + shots, I returned that copy to the shop and I got it immediately replaced with a new one. I turned the camera on and started trying again ... no change. Exactly the same behaviour.
AF was definitely not accurate and AF microadjustment SW tool did not support (Manufacturers should provide clear indications about an effective procedure to get a fine tuned focusing by mean of that feature...).
Once I managed to get a few (very few) decently focused images, I analysed their 100% crops that seemed to contain much less details compared to 40D, and at the same ISO level 50D appear to be noiser, unless you chosed to enforce NR with obvious further softness increase.
I went back to the shop and their kind personnel spend a couple of hours evaluating my pictures and shooting new ones with several lenses without achieving improvements.
They addressed the problem to (1) higher resolution sensor, (2) typical Canon softness (???!!!) experienced on pro-models that require heavy post processing, .... (God save the old 5D!).
I gave up and decided to swap to Nikon D300.
I should have kept my beloved 40D: its image quality is still unbeatable in its class and the price has decreased to such a point that this superb camera has become a bargain.
I may have been unlucky to pick up two 50D bad copies, anyway my personal advice to everyone who is planning to upgrade from 40D to 50D is to go and test themselves to the shop before taking their credit card out of the pocket, this way avoiding to experience expensive and time consuming disappointments.