I agree completely. It has an amazingly large world, and it's visually rich. The first time I walked into a shrine, looked over the balcony, and saw a gigantic statue extending many stories down-- wow. Just amazing.
But then some of the environments start to blend together. Worse, though, a lot of places just aren't itemized well-- you can raid 20 tombs, and not get any different items, talk to any new characters, get any new plot points, find any new quests. Basically, a lot of dungeons offer a lot of promise up front (I remember the one with the one-way door entrance that mentioned seeking treasure), but you get inside and it's the same group of monsters and nothing special.
Worst of all, though, is the main quest line. At first it's awesome. It pushes you into tons of new environments, so you don't mind the fetch quests. But then it's "walk over to this place you've already been, get this, then bring it back. Then walk over to this other place that's exactly like where you've already been, get this, and bring it back. Then, walk to another place that's totally similar to the first two, and talk to this person.".
So I haven't beat it, because this goes on interminably. But I'm excited about an expansion, because if it gives them time to focus on great quests instead of all the initial content and technology, it could be tons of fun.
As it is, the original game was SO AMAZING in terms of visuals, world detail, architecture (oh, the architecture!)-- but the quests eventually just sucked, and it was more fun to just walk around, see everything, then stop playing.