I thought the first episode was pretty good. The actor who plays Dexter is very good, he comes off as likable at times, but then he gets super creepy. I thought they did a good job alternating back between the two, a good balance where you would see him doing normal things and then do stuff that was totally psycho. Dexter going up against a rival serial killer looks very interesting.
Maybe a couple other thoughts....the body parts were seriously gross. I also am not that thrilled with the supporting characters. Or some of them. I'm not sure about Julie Benz as his girlfriend; she's not so bad, but she seemed a little too needy. I was also annoyed by his sister, it seemed like all she cared about was getting a promotion and it got to the point where she was really annoying me with her whining.