Well, the natural selection 2 map editor certainly has some early release quirks:
But I gotta say that after just 30 minutes messing with the program to figure out how it works, it blows Hammer out of the water. It's much more like a traditional modeling program in that it's based on editing at the vertex level, but has usability enhancements that you could edit as if it were brushes as well.
If you could make TF2 maps like this, we'd have much more organic map designs because they make it so easy to build on angles.