That was a pretty decent episode, though one thing that really bugs me is that Dexter didn't take the hair he found in Deb's bathroom to be analysed along with the water. It could easily have been Harrison's hair, which would throw into doubt whether Hannah was ever in the bathroom. This part seemed a bit weak, because we know that Dexter is fastidious about that sort of thing, so he would definitely have taken the hair too, not just left it sitting there. It just came across as weak writing.
I also find it amazing that it didn't even cross Dexter's mind that Deb may have poisoned herself to frame Hannah and make Dexter choose between the two of them, knowing that Dexter would choose her over Hannah. The season finale teaser looks good, I just hope they get rid of La Guerta, I hate her!