I never understood why would anyone want to limit him/herself to center af point only. Sure sometimes you can recompose, but as soon as you start shooting something moving, you can forget about recomposing, yet people still stick with center af point. Yes I know, center af point on low(er) end cameras is cross type, while others are not (even on 1dmk2 only 7 or 9 (I don't remember right number now) af points are cross type, while rest are not, and I never had problems shooting things flying at you at 100+km/h with non-cross type af points).
So my suggestion is to pick any point you want to fit your composition. If cameras would be intended to use with center af point only, then they wouldn't bother implementing another 6, 8, or 44 af points into them 