Oops, forgot to mention, the 600,000+ actuation camera is a 1Ds-MkII.
The only real problem we have seen with them is they sometimes "crash", i.e. they are powered on but nothing is displayed on the top LCD display. Pulling out the DC coupler for a few seconds, then re-inserting seems to reboot them and they are good to go again. This only occurs when they are powered on and off several times in succession.
No problems with shutter bounce, we do shoot in mirror-lockup mode now. (we were having some problems with vibration before). Shutter speed varies from 1/60 to 1/100th.
Also a pet peeve of mine, when you change from PC-1 to PC-2 or PC-3 in EOS Capture, it doesn't actually change the setting in the camera. Have to manually change it with that horrible wheel interface. So for now we use the same PC setting, and change the referenced tonal curve via Camera Settings in EOS Viewer.
Other problem would be that during the first few thousand releases, there is usually a ton of debris coming out of the shutter mechanism (or is there to begin with straight out of the factory. I use one of those sensor brushes, does a good job and it's fast.