found this on another forum looks like the mk3 is not up to the job ,i had just ordered one but it will take a couple of month's to arive so hopefully Canon will have fixed it or it will go back.
Rob.
http://www.robgalbraith.com/bins/co...cid=7-8740-9006
The jury seems to be out on the AF issue, Rob - for every post or article expressing concerns about the Mk III there are far more suggesting it is indeed the Bog's Dollocks - Andy Rouse raves about the AF.
But this is the risk you run in being an "early adopter" - I've done it before and will never do it again...
[QUOTE=Keith Reeder;921162]The jury seems to be out on the AF issue, Rob - for every post or article expressing concerns about the Mk III there are far more suggesting it is indeed the Bog's Dollocks - Andy Rouse raves about the AF.
But this is the risk you run in being an "early adopter" - I've done it before and will never do it again...[/QUOTE]
a lot are happy and a lot unhappy -at leaaed when mine arives we will know for sure how good it is in an exspert's hands 
lol
iv just read yet another review and he say's it's ok although it's not on bif shot's but kids running most AF digital camera's should be able to do that .
it's fine by me if it carn't get Kids infocus as long as it will get bird's :)
Rob