Yeah, most of the last few episodes have been sub-standard. Yet, there were elements here that I liked.
One... the real "threat" here - Vaughn - is a pretty good guy, leaving out the fact he insistently put the moves on another guy's girl. He was not the villain, which would have been an all too common and overused plot device.
Two... Castle does seem to have a tendency to be a bit immature and taking Beckett for granted. Consequently, this kind of rift is bound to occur. Of course... once again the guy in the relationship is again the one "at fault".
BTW... how do you pronounce Ioan Gruffudd's name?