Because I know you all are *dying* to know my thoughts about the Castle finale, (ok, maybe like 2 of you) here are my mostly spoiler free thoughts...
The episode itself was fine. I thought Nathan's acting was stellar (if you've seen it, you know what I'm talking about). I thought their reveal of the big bad was anti-climactic. There was not enough explanation
As for it being a series finale- I got closure, so I'm happy about that. It was really rushed and felt disjointed, but I guess I have to be ok with it.
I knew when they announced that Stana wasn't coming back that I wouldn't want a Beckett-less Castle, so ending the series was ok with me. I feel like ABC handled it very, very poorly. It was really disrespectful to the cast and crew who worked so hard to bring these characters to life, and to the fans who welcomed these characters into their homes every week. I would have much preferred a short 9th season (with Stana, of course) that allowed the writers to wrap up the story appropriately.