I've got a 30 hex! It's a beautiful reef. I think you actually have more options with stacking live rock, because you have more angles to view it from. You get to design "in the round." My only regret with the hex is I filled it before I realized I should have it further out in the room so I can see the backside. Now it's too heavy to move. C'est la vie.
Lighting is a bit more difficult to find for the hex, but if you get your lfs on it, they can come up with some options. I went with PC lighting that I had to special order through my LFS. I keep a few extra light bulbs around just in case. Pendant MH would be nice perhaps, but it wasn't an option for me.
Anyhoo, the tank has some nice zooanthids, frogspawn, a couple of anenomes, organ pipe, star polyps, mushrooms, assorted shrimp and clean up crew, and a tomato clown. They are all happy and healthy!