I made some comments in the breaking bad thread, but basically I felt this season was a huge disappointment. I was really expecting something other than the typical cat and mouse game with the killer. It started off promising with Dr Vogel, but it ended up just losing me.
As for the finale, I would have done a few things differently, personally. I would have had Dexter see Quinn distraught in the hallway as he did, and I'd have Quinn give him the news as he did. Then, since the idea is to throw Dexter into an "oh my God, I really can't protect the people I love anymore..." meltdown, I'd skip the scene where the doc confirms Deb's prognosis and have Dex just assume she was a goner. Reason being? The whole "I can't leave you this way" sequence from the turning off of the life support to him taking a dead body off the floor, down the elevated, across the PARKING LOT, and into his boat (all while wearing his kill shirt lol), was just extremely unrealistic and it took me out of the show. Even when there is a weather emergency, there are still protocols in place at the hospital, and there was just no way any of that would have happened. Further, Deb just deserved better...so after Dex had left the hospital, made the phone call to Hannah and Harrison, and headed out to sea, I'd have Deb open her eyes with Quinn by her side. Lastly, I like the way they wrote Dexter's fate, but I would have time lapsed the final scene about 20 years and have a rugged, expressionless Dexter sitting at the table showing significant signs of age.
Anyway...that's just me. I felt this season was more due to pressure from the Showtime execs and it affected the quality. I was on board for the first several eps, but then it slowly lost me.