I've taken a couple of days to try and figure out how I feel about this book. Definitely there are mixed feelings. The final section improved my overall attitude toward the book, and yet--and yet...
Tough topics (race relations, generational/family interactions and emotional inheritances)
Characters facing difficult situations and responding to and learning from them, even while kicking and screaming
Very ambitious undertaking
That Obama cameo that didn't really fit the book and seemed gratuitous
That 12-page sentence that didn't really fit the book and seemed gratuitous
Subplots that detracted rather than added to the story
Some bizarrely wrapped-up things in the ending (I don't want to give spoilers, but I did not really buy the resolution of the lawsuit against Gwen and Aviva)
Some characters deserved more time than they got, apparently in favor of some of the subplots (as in, I'd really rather have spent more time with Nat and Aviva then in Luther Stallings' criminal capers)
I think a lot of people will disagree with me. I think others will nod their heads in agreement. And I think this is going to be one of those books people are talking about at the end of the year, and it could easily show up on the 2013 Tournament of Books. Put up against some of the other 2012 releases that I've read (Arcadia, Gone Girl, The Fault in Our Stars), I'll admit that the Chabon book is more ambitious, but overall I felt that it had more stumbles and left me not loving it, although I didn't hate it.
I guess these are good times for readers when I can afford to be so picky about what I love.