Blenders interface is built with power users in mind. They've made some progress in reducing how steep the learning curve but they still have a ways to go.

Your right about how clean/responsive and fast it is. They have justifiable pride in how many features they include in such a small binary. When I was hacking on it Blender weighed in at under 10 megabytes with features other apps needed 100s of megabytes to provide. I think they still come in under 20 but I haven't checked in a while.