I received one of the first 1DMk4 production bodies in Asia and have been using it extensively shooting professional tennis (all with f2.8 lenses) in two countries since then, shooting both in very good daylight and under floodlights. The results can be seen on Maria Sharapova and Venus Williams' official websites. The results so far for me have been excellent with AF in daylight but extremely poor (the same poor, and possibly worse! AF success rate as the Mk3!) under floodlights, both with out of the box focus settings and with the AF setting adjustments (for sports such as tennis) as suggested in the Mk3 AF adjustment document issued by Canon last year. Once users receive their Mk4 and have tested them, pls share your AF experiences for fast moving sport under floodlights as I am trying to ascertain if my particular Mk4 is a dud or if we will all be experiencing the same ugly AF issues for fast moving floodlit sport with this otherwise very nice camera.