I ended up watching the first season of Dexter over the weekend, and I figure to make it a quasi-recurring feature to review shows that I've watched, spoilers within.
Overall I enjoyed it. I found Michael C. Hall's voiceover and portrayal as Dexter to be both the show's best part, and its worst. Not worse in that he's either terrible or terrific, but worse because he's way better than the rest of the cast. To be honest, I'm not entirely sure it's because Hall is a better actor, or if he's just getting better writing, but either way, the rest of the cast is fairly "meh" in comparison. The book that the first season is based on is written solely from Dexter's point of view and I suspect that's part of it, they know who Dexter (sorta) is, while the rest of the cast are just ciphers, as alien to the writers as they are to Dexter (from what I understand) in the books.
The subplots with all the characters not named Dexter come off as tiresome and generic, and the writers, for the life of them, can't write a decent female character. Dexter's sister is incompetent and tries to sound too much like a tough cop (which I understand is the character, but the acting itself is pretty atrocious, since she doesn't sound comfortable cussing at all. One critic said (derisively if you ask me) that essentially her acting vulnerable and uncomfortable is so good, that the audience faults the actress, instead of the character, which I call BS on. I bring up the cussing only because they decided to make her foul-mouthed, which would work well if the character was trying to do that to seem like a tough cop, but she does it with everything, even with her boyfriend, around who she lets down her guard. The female lieutenant, LaGuerta is conniving and totally incompetent, as is her replacement who devotes police resources to stalk her fiance. Rita, Dexter's girlfriend, is the stereotypical once abused character, which the writers sort of ruined with the return of her ex-husband, when they made him too good a guy, and too sympathetic, making her seem whiny and petulant. Granted, the ex-husband's assault on her was brutal and all, but they're attempts to make him menacing and evil just... didn't really work (and when they tried to guilt the viewers when he died, it made him, again, too sympathetic). Julie Benz, who plays Rita, does well in the role, I just don't think it's a particularly strong one because of the script.
The one element of the show that I thinks works best, as I said above, is Dexter's voice over. The narration helps understand who Dexter is, since he can't show anything with other people, as he's a sociopath, and can't be be found out, but more importantly, the unreliability of it subtly twists the show. Being able to watch, and realize that he's lying to himself about something, or see his actions belie his thoughts, makes the show a little better than Dexter the entertaining serial killer. Now, granted, this could just be a personal reading, the writers could intend for his narration to be on the level, but I don't think that's the case, too many things don't quite fit.
Overall, I find the series to be solid entertainment, it's good, I'm willing to watch, but I find that I don't quite see what all the fuss is. Yeah, Dexter, the character, is entertaining, but watching the excruciating B-plots (I admit that I always enjoy watching Doakes, because he is just that laughably bad), and realizing the show is... maybe not quite misogynistic, but certainly not kind to females, makes me wonder what I'm missing...
On a side note, I've watched the first half of the second season as well, and generally have an idea of what's going to happen to certain characters. So far the second season has been a "one step forward, two steps back" sorta thing. I'm hoping season 3 is better, though I'll probably stick with it, since the 4th season has John Lithgow. Also apparently Lundy returns, who enters the very small group of decent actors in Dexter.