The only book/series I ever hated is Robin Hobb's. I read the first trilogy and I was so pissed off at my self for not dropping it after book 1. The main character is so unlikable for me, I was hoping that he would redeem him self by the end of it...
Well his wife was his editor, so that could have been it. I don't know, while I do agree that the books could have been slimmer, I didn't mind slogging through mud to reach the pearls. I agree that Sanderson did a good job, Mat's POV notwithstanding, but the last battle would have been so much more epic had Jordan had the chance to write it. I still haven't come across a book/series that has battles/action scenes as...well...EPIC.
You should give Sanderson's Stormlight Archive a read, it's pretty good.