You do realize that your signature is out of date.
On topic: I think that the biome generation is fine, cuz lets face it minecraft isn't the most realistic game anyway.
Realistic or not, it's annoying to have rivers with breaks in them. I'd like to be able to navigate down a river in a boat without having to stop and make a new boat, or dig a canal to connect the disjoint segments.
It's not really about realism. Minecraft's biomes are nothing like our world to begin with.
The real point that is being made (albeit a bit rough) is that the transitions between biomes should be made smoother to make them look a lot more appealing.
There is a difference between artful parody of the natural world, and just plain sloppy game design.