I'm with Lil and LFL on the rarity of O'ing together. Just speaking from my own experience I can only think of one time I actually O'd at the same time as my partner, but I actually had just began O'ing then he did...so it ended up simultaneous that way.
I agree....the necessary motion usually is interrupted when the man O's to continue to get the woman there at the same time....so that usually, well....kills the O for me. I totally enjoy having them separately. For me it makes me feel so special to have my H concentrate on me completely, and then for me to concentrate on him and fully get to enjoy the experience when he O's.
