I've been generating tons of seeds this evening, and one thing I've learned about 1.7 is that the biomes are big (even in "normal") and spread waythefuck out. I'm going to keep trying to find a seed that has all the interesting biomes (ice, mesa, mega taiga, savanna, roofed forest, etc) within a 1000-block radius, but it's challenging. Since adjacent biome placement is actually more logical instead of random, it's far more difficult to find variety within a given area.
Some single biomes span over a thousand blocks wide. The entire area of Cashout Cove that we're keeping is a "mere" 1.5K by 1.5K blocks. Some of these new biomes could swallow the whole area!
We may simply end up having a world that lacks one or some of the cool new biomes...