I loved it but had many complaints nevertheless.
First of all, I'm disappointed to see that the "Deb loves Dex" stuff is still going on. I was hoping that she'd realize that she isn't in love with him and that somehow it would lead to something else, more interesting. The scene with the therapist was well-written and well-acted though, so I can't complain too much. Here's to hoping that the next season finds a way out of this.
The Angel/Quinn stuff didn't feel like season finale material. I just didn't feel like Quinn's position was really threatened and I hate how we weren't given a definite answer about Quinn's fate. I hope the writers give them something better to do next season.
My last complaint is about how short the Dexter/Travis confrontation was at the top of the skyscraper. I wished that they had fought more after Dexter "injected" himself, it just felt like Dexter knocked Travis out way too quickly.
Aside from that, I loved pretty much everything about the episode. The opening scene at the sea with the boat was fantastic. I also loved how there's huge emphasis on Dexter and Harrison (just like the first half of the season before Brother Sam died and things went off-rails), not to mention that the music playing was absolutely beautiful!
The Dexter and Debra interactions were actually well-written and that scene when they were examining the two bodies and acting all weird was quite funny. I also loved Debra & LeGuerta's interactions. I've always liked LeGuerta and don't want her to leave the show unlike many other fans, she always brings a sense of unpredictability to the show and acts as a counterpart to the boringly-good Angel, for example.
Dexter and Travis' final conversation was just epic. It was incredibly well-written and I especially loved Dexter's line "I'm a father, a son, a serial killer". The last 10 seconds had my jaw on the floor! I mean, I had my doubts about Debra showing up but it was still shocking! This moment has been six years in the making after all.
I have faith in the writers to deliver great storytelling next year when it comes to Debra dealing with Dexter being a serial killer, they always write their scenes better than anything else. I just hope they find a way out of getting them into a relationship or whatever...