Good job everyone! I'm giving it a 4/5. It gets 1 point off for being, like others have suggested, inconsistent in terms of funny. Still, I can tell a lot of effort was put into it and it's overall much funnier than AMV Hell 3 I think.
It seems to me that AMV Hell 3 had all of its good stuff up front at the beginning and after that it tapered off into crap (until the hilarious credits sequence at least). This is much more balanced all the way through. Instead of starting good and ending crappy, it more or less just bounces back and forth throughout the whole video, which is better I think.
Anyway, the segments that stand out in my mind:
Death Note - Pinky and the Brain/L is for Loser
Azumanga Diaoh - "Cowbell Hero"
One Piece - Yackety Sax/Popeye Theme
The Melancholy of Haruhi Suzumiya - Black Winter Night
I also liked what you did with opening/ending segments. They made for a great review of the AMV Hells. As far as having too much Azumanga Diaoh and/or Death Note, well, neither one really bothered me. Most of the Azumanga Diaoh clips had some pretty fresh ideas and, well, I never watch Death Note AMVs so those were all-new to me.

Again, good job. I regret that the segments I did didn't make the final cut. Congratulations to the rest of you!