My first one was defective in some really odd ways. If you let it go to sleep for more than a minute or two, the back LCD wouldn't wake up. You could adjust settings and focus as much as you wanted and see that they were taking effect from the top LCD, but the back LCD never lit back up and the shutter refused to trip. Also, the zoom in/out buttons when viewing images would zoom out (yes, even the zoom in button) for a fraction of a second and then come right back to where you started.
I ran it back down to Cardinal Camera in Lansdale. They agreed that it was pretty much possessed and in dire need of an exorcism and happily swapped it out for a new one.
After shooting with it on the lake this weekend, I can say I'm extremely happy with the upgrade. Wildlife and sports will definitely be a bit easier with the faster and more accurate auto-focusing, better higher-ISO performance, and the ease of control as compared to the 400D.
