The outer points are the weakness as Neuro says. I use center spot and recompose.. it's second nature now. Center point is accurate. If you do not want to recompose, then it will be a hit/miss scenario.
Agree, the centre point on the 5D2 is brilliant and highly reliable. But it's the only one you'll ever want to rely on. My experience with using the outer AF points, even on bright, high contrast subjects has been consistently underwhelming. With portraits where I really want the focus point right on the eye, the outer points frequently deliver soft results, or results with the focus point in the wrong place.
Next that brings us to the dreaded "focus & recompose". Sometimes you'll get away with it. This is dependent on your current focal length & camera to subject distance. It's best explained in these articles on "Why Focus Recompose Sucks". The only camera where I'll use focus/recompose is on a far more forgiving point and shoot.
Which brings me to one of the major reasons I choose to shoot most jobs with 1-series bodies with 45 focus points. A 5D3 with a comprehensively expanded powerful AF point array would be an instant buy for me, primarily because of the reduced weight of a 5x vs 1-Series.