I had to send my 40D back for factory service. 
There was an obvious mark on the IR filter over the sensor when I first got it that would only show on pictures in the right circumstances and wasn't much of an issue, but I would have sent it back eventually (I didn't notice it till after the return period had expired otherwise I would have exchanged it).
But starting yesterday, the unit would no longer power on with a fresh battery (and the tabs on the compartment doors pressed).... so I sent it to the Irvine repair facility yesterday.
Here's hoping for a speedy return, and yes, my first picture upon receiving it will be a duck. :P
