My favorite two places to sit in Wrigley are either in the 400 section, preferably 417-420 (right above home plate, and right below the pressbox) or in the bleachers. The 400 section for the view of the game, and the bleachers for the drunk of it.
The downside to the bleachers is that if you have to make a trip to the bathroom, prepare to miss about an inning of action each time. And figure on missing about a half inning to go on a beer run. Also, you have to get to the stadium at least an hour before the gates open (a total of three hours before the first pitch), if you want to have any say as to where you sit.
That being said, some of my best times have been in the bleachers. I was out there when Kerry Wood hit his HR vs the Marlins in Game 7 in 2003, and I've never experienced anything like that in my experience of attending sports...