Yeeeah I didn't enjoy their cheating storyline in s3 either. It felt so out of the blue and out of character as you guys said. I think there were indications prior to that that he may have liked Willow and didn't realize it, but they waited too long to do anything about it.
Anyway, watched "Some Assembly Required" last night and I liked the XW scene toward the end of the episode when he asked her if it felt like they were playing musical chairs and everyone got a chair but them. Then Cordeila walks up trying to thank him for saving her life and he's like, "we're trying to have a conversation here."
