Excellent start. I figured they were probably going to play Dexter into a spiral but to take it so far already was pretty shocking. Dexter has dug himself a pretty deep hole with his off-the-code murder of that jackass and his strange behavior towards the FBI and his family. One can only hope that he was able to dispose of the crime scene properly after his post-kill rally. He had the boat nearby, so maybe he was able to dispose of the body unseen. I think this is not at all certain based on his state of mind at the time however. I hope they'll come back to this, otherwise the details will continue to nag at me.
I'm enjoying the use of Harry at this point in the storyline. Dexter needs a co-conspirator, and so he imagines one in the form of his father. Yet this Harry is not really speaking as his father any more, and is increasingly starting to sound more and more like Dexter himself, speaking the things that Dexter is not yet willing to admit to himself consciously. It will be interesting to see how far they go with this.
I thought the flashback as goodbye scene for Rita was touching and well played.