Gosh I hated that guy so much. Mikami was just a bad character, but I guess that's what he was designed to be.
Regarding Near being smarter than L. Well, I don't agree with it, and like Oreki said, plot did a bad job of showing it if he really was. Plot made it seem like Near just guessed everything correctly out of luck. Not to mention L laid a lot of ground work for Near and Mello to work with.