If the money and space are not a problem for you, I would sugget 3 feet high as it does nothing harm. But in general, 30" will be a good size. Only my personal opinion.
I'd agree with the fact that they look great.
One draw back to a tall tank is maintanence. I've a tank long the lines of 3'x3'x3' and it is just a pain to do any work inside the tank. Hard to reach everything and you're always up to your armpits in water.