Also saw it in London; it was fantastic. The staging was a technical marvel. The story was very well-plotted for its three-hour or less running time, largely keeping the focus on the hobbits. It definitely had an epic feel, and got very moving at times.
My one quibble was that Gandalf was a bit of a jerk. He did a fair amount of exposition, and had to speak quickly to move stuff along, and while the guy was obviously trying not to copy McKellen, the Gollum guy was just as obviously doing the movie version.
Oh, and it woulda been nice if they'd licensed some Howard Shore music. A lot of the battle-type score was loud and mythic without having the film score's sense of purpose. And the songs were largely forgettable.
Okay, that was more than one quibble, but I still thought it was an awesome show. Especially when you've got free tickets.