Thanks for the links. I looked at the video and in my case wasn't that blurry (and not particularely for close-ups). The problem is just that patches of grass were smeared when zooming in just a little (after taking the shot).

Moving to the pro format solved the issue, so my guess is that it's more a problem with the compression / post processing than with the auto-focusing part (although i must say i'm not really sure what constitutes post-processing anymore with modern camera)