Well I don't know about House becuse it does nothing for me, but really I was perfectly fine with the way Castle ended.

The facts of the series (or episode) were
Castle needed to finish book
Kate had commited to a relationship with whats his name
Castle decided to bow out of the compition to woo said Kate and decided to focus on his job of writing.
Considering that his ex is his publisher, he needed focus she is the perfect person to join him at the Hamptons. (side note I wonder if he will use the Concierge doctor while there?)

All in all a perfectly logical ending, Castle is trying to find happiness in his past, Kate is left in the lurch with no partner.

Season Three will probably start with the book launch and some case will come up where they need his specific help and the sexual tension can start up all over again.

Usually one of the worst things that can happen to a show is for the protagonists who have sexual tension to hook up. One other show has done a pretty good job of managing it so far though.