I've read it, but I'm not going to review it here. Partly it's because I don't feel quite up to the task, and partly because this book really doesn't need any further help from me. Of the several things I've read about it so far, I think this New York Times Book Review piece by Sam Tanenhaus was the most helpful, though I'd recommend reading it after you read the book rather than before.
Personally, I would and will read anything Jonathan Franzen cares to write, just to make my own position clear.
I thought instead of a book review, I'd mention something funny that happened a couple of nights after I finished the book. I was watching a performance on PBS and one of the characters gleefully said "Freedom for everyone!"
What's not to like, right?
Well... that character was Don Giovanni, surely one of the archetypal villains and libertines of Western Civilization. And as a matter of fact, there is a Don Giovanni type in Franzen's book, in the character of Richard Katz, punk rock star and seducer, though by no means as black and white or one dimensional a character as the Don. In any case, this particular vision of freedom is one of the many types that Freedom is written to illustrate and explore, so I watched the rest of the opera looking for parallels.
During an intermission, there was a brief interview with the conductor, Donald Runnicles. He said that at the end of the opera when Don Giovanni has met his just fate, it's interesting to see that the other characters are left with a kind of blank space or vacuum in their lives. And it's certainly true that Freedom would have been the poorer without Giovanni's latter day avatar. What this says about demonic energy, I really don't know.
Read the book.
(The cartoon, by the way, is from a site called Head Injury Theater.com)