I've been watching it (episode 6 was this past Sunday) and while there's a lot to like about the show, there's some things that I really don't like about it. A minor complaint is that his sister cannot say a sentence without "fuck" in it. I have no problem with foul language whatsoever and it doesn't matter who utters it, male or female (Deadwood, my all-time favorite television show, being the proof that I'm not easily offended). But the sister's non-stop cursing in Dexter is gratuitous and distracting, for me anyway.
On a more serious note, I have a problem with the idea that it's okay to kill "bad" people and Dexter gets to decide who's bad. Case in point being episode three when he planned on killing the kid who had just been released from jail but then chose not to when he found out the guy the kid had killed (which got him into jail in the first place) had raped him. Somehow that made it okay to kill the rapist. And when they parted company he more or less admonished the kid to only kill people who deserve it.
And yes, I understand that by virtue of being a serial killer, Dexter himself is a psycho and his particular standards for who lives and who dies is not being promoted as some kind of general behavioral guide. We're being given a look into the workings of a truly fucked up individual and no conclusions ought to be arrived at as to the merits of vigilante justice based on what we see. Still, the show's premise leaves me with something of a bad taste in my mouth.
Those criticisms aside, it sure beats the hell out of 99% of the crap that passes for television entertainment nowadays. And there is something to be said for being disturbed by a show. Most of the shit on the tube doesn't register a reaction with me beyond wanting to change the channel. Plus the music that plays over the credits is supremely creepy.