The thread is spoiler marked, but here's another spoiler warning since I'll be discussing the entire series. If you haven't watched the entire thing, leave now.
First, Light is fucking epic. The man manages to manipulate all sorts of people, include FBI, the world's greatest detective, and even a Death God. The entire series (almost) is an example of epic level intellects and social skills in action. He's even willing to do some ballsy things like threaten an FBI agent in the open and not get caught. And he looks so casual doing it!
Now that that's out of the way...
It's suggested at the beginning and elaborated on later that Light was actually a pretty good guy at the beginning. Just like his dad. It's interesting to see how the notebook transforms and corrupts him, and the Light/L conflict drives the first 14 or so episodes and makes for a very interesting battle. It becomes increasingly apparent Light is actually smarter once he stops making stupid mistakes. Episode 15, it apparently goes all to shit when he's stopped a second way from getting L's name, then the captivity thing kicks in. That makes for multiple pretty bland episodes, especially since the new guys are really stupid despite their positions in the world and get themselves caught very easily, not to mention give L far too much information. The elaborate gambit, and manipulation of multiple beings pays off though and he finally beats his rival. Naturally, things are interesting again. The replacements for L... meh. Not nearly as entertaining, or as capable. Still though, having Light back to how he was makes watching a lot more entertaining. Misa seems more intelligent and less annoying as well.
But then at the end, one fuck up costs everything. And that's just a damn shame. If only he had stayed silent for a few seconds longer, and figured out the second layer of the trick that he should really know better about he would have been fine since he could have ordered that guy to put every name including Light but excepting N. What's more, the multi layered tricks were his thing first. Eh. Now, that would have been interesting because then it would seem like N is Kira. Hell, the fact the incompetent oaf who actually liked Kira (Matsuda) had to be the one to do it is disappointing enough. But even then, if he had another note on him, or was going to get one it could have still been a good ending because then he could have taken his enemies down with him at least. Or maybe Ryuk could do it. It's not lengthening Light's lifespan if he kills them and Light, is it? At least then the guy would get the last laugh, ya know? I am very disappointed with the ending. Yeah, dying with some dignity is nice, but being thwarted by the team dolt is not.
And the second opening is nowhere near as good as the first.