I prefer Kuro/Fai (and see the manga going in that direction) but I wouldn’t particularly mind Kuro/Tomoyo and/or Ashura-ou/Fai instead. The one pairing that I really can’t stand (obviously, since I’m in this thread) is Fai/Chii. Even if I knew nothing about Chobits, it still would make no sense. Fai turns her into a net, leaves her protecting a man he’s running away from, makes a wish to never return to his country, and never once thinks about her after that. It’s even to kind to say that he loves her like family.
The whole Chobits matter makes the pairing unbearable, though. Hideki/Chii wasn’t my favorite pairing (there were several more interesting characters) but a whole series was based on their developing relationship. Why would that be broken up? Especially when CLAMP, if they wanted Fai to have a romance with a creation, could have used Freya, who is both without a soulmate and has a creator complex. No, CLAMP isn’t going to break up couples – they’ve kept all of their soulmates together so far (Shouga/Primera doesn’t count.) So why would they just pick and choose which pairings stay together? It doesn’t make sense. I'm really defensive in this area, since I'm reading the series mostly for the crossover side characters.
On Chii’s side, she shows some sort of gratitude for Fai making her, and some confusion, but none of the heartbreak she felt when she though about Hideki leaving her. Also, Hideki not being shown so far doesn’t mean anything, as we haven’t seen Chii either.