There have been three main problems we have wanted to address:
Too large oceans
Too uneven/random biome placement
Not enough variation
Too large oceans? Booo... I like the large oceans! I love the idea of sailing somewhat endlessly. Although I do like the idea of adding more islands.
I will agree with uneven biome placement. It is much more natural to progress from taiga to grassland to swamp, to jungle, for example.
Variation... I dunno. The Minecraft world can get pretty big. I think variation wasn't too much of an issue.
It is exciting, though, and I think I'll be rejoining the server soon.