Dexter as a hybrid style of show. In one sense it is quite a shallow variant on police procedural - 'high concept' - an idea that can be summed up in one sentence: 'What if a police pathologist were a serial killer?' The sort of naff-but-successful idea that Charlie Kaufman's dumb screenwriting twin would come up with in 'Adaptation'. And then the working out of that concept is itself (in some ways) shallowly conceptual: the script sets itself problems, forced on it by its own internal logic, and then solves them.
Dexter must never be caught; Dexter must never do certain things, and these must be prevented by some sort of reasonable plot exigency; Dexter must never violate certain emotional taboos of the audience, while ostensibly being without those emotional taboos himself; Dexter must constantly give the game away and be misinterpreted by the well meaning souls around him. It's as stylised and non-naturalistic as a Pantomime. And they do make that into a joke in itself anyway, so no harm done.
However, into this very cutesy context, they do drop some jolly good writing and acting. For example part of the cutesy formula is that Dexter tends to learn a little moral lesson from each one of his victims, one way or another. And this is done with quite a bit of class IMHO. Last night I watched the episode where Dexter goes to Narcotics Anonymous, and there's a cutesy bit of writing where he talks about his addiction to killing, in such a way that all the addicts believe he is talking about heroin. It was 'clever' in a superficial sense, you know 'pats on the back all round', but I also think it was well written and well performed.
So I would say the writers have got a lot of class, and they drop nuggets in which seem to come from a more ambitious show.