Allen,
As a working pro know that Pete Souza, President Obama's White House Photographer, decided to use Canon's for those 8 years. His reason for selecting a Canon DSLR was because it had the quietest shutter.
I attended a show at a 600-700 seat auditorium to hear a presentation that was sponsored by Photoville where Pete described the 8 year experience. He shot over 2 million images over this 8 year period. I imagine he wore out a few shutters and destroyed some gear along the ways.
BTW he always carried two cameras, and over the eight years he said he only took one week's vacation and was only used one sick day.
The presentation involved describing certain shots that I would deem not only historic, but also iconic. I do not use the word iconic lightly, and to me iconic means you can see an image once and you will remember it the rest of your life.
One image was in the situation room when SEAL Team 6 took out Bin Laden. A detail was revealed and discussion about the open lap top in that shot because it had classified information.
Also he had a book coming out and talked about how he culled and edited from that library of 2 million pictures.
At the end of the presentation someone asked what his life is like now. He spoke of being mighty tired.
Another iconic shot is with Bono playin the beatles song "Norwegan Wood" with Alica Keys in the background. President Obama had turned to Pete and said, "Can you believe this?"
Bono previously asked where he should sit, and President Obama said, "Anywhere," and that is when Bono picked up the guitar and started playing.
So all these concentrated anadotes...
About half a year later the book was available.
I have a Nikon F5 and as a badge of honor one day I jammed the shutter. Pretty much even though the camera is clean, the shutter I would say is likely worn out.
Cal