The problem I have with Minecraft's biomes is the word "biome" (which means "climate zone", btw). It's too close to "Boom", which means I end up singing "Biome, biome, biome, biome, I want you in my room!" whenever I read it. Mojang's problems with the biomes, however, are a bit less childish: the rules used to create variety in Minecraft's world generation means there's often unrealistic placement of zones. Desert and snow bump up against each other, there are uncrossable oceans separating continents, and there's not enough variety between chunks. Version 1.7 seeks to change those rules.
Mojang will be tweaking the creation of the world, steering it away from worlds like this.
And into worlds like this.
If you squint, you can make out the logical progression between areas, and obviously the oceans are smaller. Minecraft's project lead Jeb has promised that there will still be biome collisions, but they'll be much rarer and worlds will mostly conform to these rules: "Biomes have been put into four main categories: snow-covered, cold, medium, and dry/warm. Biomes will avoid getting placed next to a biome that is too different to itself (sometimes this still happens, but it’s very rare now and not all over the place)."
These problems they're attempting to fix have existed for a while. Minecraft creates the world in chunks as you move through it, and the longer you walk, the more world is created. So when Mojang change world generation rules, it can result in strange transitions between old chunks generated with the previous rules and new chunks loaded under the new rules. That never bothered me, and I kind of like my worlds abstract and broken. But with the 'problems' dealt with all at once, new worlds will be more consistent. I get that most people enjoy consistency, but this looks to be a little bit too ordered for an explorer type.
I might take this up with Jeb personally, as he's in the Victoria & Albert Museum in London tomorrow, talking about Minecraft at an amazing sounding exhibition.