The ending was extremely dissatisfying. I think the last section and ending were the biggest example of this lazy/convenient writing, with a pacing style that was all over the place and ludicrous story conveniences or complete removal from logical outcomes.
It's not as if I wanted Light to win or anything, it's just the way he lost was kind of absurd. His approach to things is extremely methodical, you'd even expect Mikami not to make such a stupid mistake. It's as if Light's hubris led to his own downfall. Classic fail of the tragic hero, something straight out of Shakespeare.
Also one thing was that I just couldn't relate to any character towards the end. While the show had me hooked, I hated every character in Death Note. L and Light were no different -- both were arrogant. Near was even worse. I think Ryuk was the only character I found enjoyable -- but his screen time waned considerably in the final few episodes. It was Ryuk's game after all -- he started all this. But the focus almost disappeared from him and the fascinating interactions between him and Light were non-existent at the end. He was one of the best parts of Death Note and they gave him nothing of substance after episode 15 or so. I feel like the writers were too lazy or wanted to go in a different direction, to delve into anything of substance and this great character paid the price. Such a shame