I have! I was in the house right box. It is very close to the stage and gave a relatively good view, but if I had a choice I'd go with the house left box instead, because Lily Garland's cabin on the train is on stage left, which is slightly obstructed from the house right box. Lots of action and humorous bits take place there that you partially miss from the house right box. Otherwise, they provide a very close view of the stage and performers.
There is an entire thread on this subject, somewhere. I figured I'd just weight in here :)