I tried before and went back to change to other stuff instead. YOu will lose all the feel to the buttons and the hot shoe protector is damn difficult to remove to put on the flash. I heard from the shop some ppl even cut it off.
Hope that my experience is useful to you. The protector is not cheap either.
i have one for a 5D mark 1, and i used it when i went australia outfield for a month. basically the pros and cons are:
-improves your grip on the camera
-makes the camera a little 'fatter' cos of the extra layer...feels good to hold it but might be subjective.
-protects against stuff hitting onto the camera (e.g. stuff in your bag, stuff in the car, etc)
-gives you a little more confidence to shoot in bad weather
-the lens armor thing is quite useless (at least on bigger lenses, i used a 24-105mm)
-when water droplets get inbetween the case and the camera, it is SUPER hard to clean it up.
-like all silicon cases, they degrade after time and become a little stiff.
-takes a while getting used to the buttons cos they are now covered (you gotta really know what buttons do what)
-hard to change batteries (at least for 5D mk1 it was blocking the battery door)
-maybe a little hard to constantly change lenses as smoothly as without the case
whatever it was, i took it out when i came back to sg and it felt like my 5D became a 500D...felt a lot 'skinnier' LOL!