I'm usually bored by clip shows as i know all the scenes and the episodes are boring "Remember when *cue clip*" arrays of scenes.
However this one was quite good.. yes, it contained clips from the past seasons (some of them amongst my favorites) but the story of the episode was also quit engaging. Castle was willing to die together with Beckett and if that ain't the ultimate proof of love i don't know (we'll conveniently forgot the pain he'll put Alexis and Martha in
I really loved how they used some musical cues for certain scenes especially when it's about them kissing that had the music from the season 4 finale where they finally kiss as a couple
Oh and Gates.. "Do you believe i'm an idiot?"
That was equally brilliant as with Martha back in the beginning of the season where everyone wondered how she could miss naked Beckett in the closet (and she didn't). Gates really is a pro.. she knows that she has a very good team with Beckett and the gang but Castle adds that last ingredient that makes them unbeatable so she's looking conveniently away but there was no chance in hell she'd miss the more than good colleagues behaviour of Beckett and Castle.
All considered this was one of the better clip shows i have seen.