I don't know how to do the spoiler thing. Spoilers ahead.
I actually recently finished the anime as well (thank you Netflix Instant) and I have to say... I completely disagree. Sure, the first 20 episodes are FANTASTIC, and the episodes immediately following L's death drag somewhat, I really liked Mello and Near. Yeah, Mello was a massive prick, and I wanted to see him die, but he was still an interesting villain, almost an anti-hero. You also seem to be under the impression that Kira was right, even at the end. It's pretty clear that he's gone bonkers-evil by the end. Yes, crime rates were down, but they only stayed that way while someone was active as Kira (info is from the TV Tropes page, I don't recall it in the Anime). As soon as he went inactive crime rates returned to their normal levels. And it's not Like Light lived by any sort of code. Anyone who he personally deemed evil: dead. Anyone who got in his way: dead. Anyone who had information to give him: dead. It's frankly disturbing that you view someone who, at his very best, was morally ambiguous as some sort of righteous hero. And as for Light's panic in the last episode being "out of character," well, that's only sort of true. Light came dangerously close to giving up when he thought L had caught him. Not only did N catch him red-freaking-handed, but EVERYBODY was a witness to it. It's never suggested that Light is completely devoid of emotion, and nobody with emotion is completely above panicking. No matter how much they're convinced that they're God. The whole point of the show is "is it really worth it?" and the answer it gives is "No". And it's also pretty clear that Mello and Near together easily outclass Light, so no, they didn't let the message get in the way of the plot. Unlike certain other shows which shall remain nameless.