Death Note is pretty great. I haven't read the manga, but the anime series is one of the two main shows (the other being Elfen Lied) that got me into anime in the first place.

For me the most enjoyable part of the show was the battle of wits between Light and L. It's quite rare that you see an all-out battle between two opposing sides on equal footing like that. It's almost always that one side is not taking it seriously and just playing with the other side (looking at you Gurren Lagann). In that way Death Note is pretty unique, although that is also why I felt the latter third of the show wasn't nearly as enjoyable as the first two thirds.

I liked L more than Light. L was quite ruthless at times, but very likeable. Kira was just presented as so... morally black. No shade of grey. Just black. And I prefer my anti-heroes grey, which is why I ultimately prefer Code Geass and G-senjou no Maou over Death Note.

Still, Death Note is a classic, and a very good and gripping series.