An excellent thriller, with a few caveats:
1) This is not a "big idea" book. Don't expect something like Anathem or Cryptonomicon. It's "just" a thriller, but an excellent one at that.
2) If you're going to read this book, I suggest you read it in the next six months or so. It contains so many contemporary tech references (Facebook, Twitter, and more), that I'm sure it will look dated in five years. Parts of it read almost like a tech blog with a plot, really. Still, lots of fun and definitely interesting.
And now for the good parts:
1) At over 1,000 pages, this is a lot of book for the money. The plot is intricate and stays interesting all the way through -- there were no parts where I felt I'm getting bored.
2) I liked the characters, and as usual with Stephenson, the research felt excellent. Many of the locations are intricately detailed, in a way that made me feel like he was actually there and took notes.
In short, this is more Interface and less Anathem. Not a bad thing IMHO, and I warmly recommend REAMDE.