Focus and recompose leads to back focusing if the plane of focus is really a plane. The problem is most noticeable, roughly speaking, with wide primes focused far off center, with a subject close to you. Then you can use the outer points. In good to moderate light, they focus reliably even on my lowly 5D2 with, say, the 50L or the 35L. I still focus and recompose even with those points. In really low light, I would not use them.
About cross or not cross type - the proof is in the pudding. It just works, at least in most cases.