After a bad experience with a Nikon D3, I tried my first Canon, the 1D MKIII. WHAT AN IMPROVEMENT. The focus was blazingly fast, much faster than the D3 I had used for low light. Buttons were laid out better, especially things like ISO.
IQ from this beast is second to none. Much more lifelike than the D3 or any Olympus cams I have used before. Out of camera the images are insanely sharp. Also, noise at high ISO's is non existent.