It was reliable for me but I used the centre point most of the time. People were saying the outer points were not as reliable. I did not do any testing but when I occasionally used them they were fine. However I was using f4 glass so I can't say how faster lenses AF did.
It really isn't the speed or accuracy of the 5D II AF that is the drawback; it simply cannot consistently nail
action, no matter what focus point or tracking is chosen. It is perfect for still subjects, however.
A true scenario that repeated again and again in different variations: I would shoot environmental portraits for a newspaper and ask the guy to walk along a pathway or hallway. One frame would be sharp, the next three would be unusable, the next was so-so, the next frame was sharp, the next two unsharp.
Another time I was shooting 70-85-year-olds playing senior basketball. About half my stuff was useless. (These guys
aren't that fast, folks!)
What finally made me sell my 5D II bodies was an assignment on birding in the Katie Prairie in Texas. I missed at least 75-80% of my shots, even with a 300 f/2.8.
So, the 5D II is a wonderful still camera, but a real dog for action photography. But if you shoot stills, it is great. It was also the first camera to incorporate HD video--a huge breakthrough.
--
photojournalist
http://craighartley.zenfolio.com/