In terms of the water height... its something i've heard a lot of people ask for, myself included. I believe they will be doing a big water update in the updates to come from what I read a little while ago.
For me caves are not important as I'd rather construct them using cave hall way segments/pieces. Its lighter on memory that way. Rather than cutting into the terrain.
i7 -2600 CPU @ 3.40GHz - Windows 7 - 8GB RAM - Nivida GeForce 420 GT