Jeffrey: The first thing they get is, essentially, an entire new area called Eregion where book 15 takes place. That's even before you get into Moria, and it is available to everyone in the game regardless of whether you have the expansion or not. I think there is only one area out of ten new ones that is inaccessible without the expansion. That, of course, is the part of Eregion that leads you into Moria. We added some functionality to the game, too, with things like tradesets and other things.
All of the polishing/tweaking/balancing we've done to the game, whether it is class balance or smoothing out animations, all of those are available to anyone playing the game period. Getting into Moria itself, the new classes, the new levels, and the legendary items are what people are really buying the expansion for.