I find them having a good size, but I think there should be more different sizes rarely. Where are actually giant deserts? Plus the lack of elevation change makes it kinda bland.
No. I want to prepare food and materials for a massive, week-long trip across the ocean to new lands. I want to start in a massive desert biome and eventually die in a massive desert biome! If anything, they need to be bigger! MUCH BIGGER!
I don't like a big project being on 3 different biome. 1 end is in a desert, the other is under snow. no thanks.
Notch just needs to make sure that you don't start on an empty small island without wood in middle of an ocean like I did several times.