Kasey has a really interesting post on Aikido here. For those to lazy to read it, it boils down to the idea that he's learned a lot of applications of Aikido concepts from people who don't do Aikido.
Which pretty much mirrors my own experiences with that art. Awesome set of ideas and concepts, attached to a decent training methodology, which is populated by people who largely don't want to experiment, change, evolve, or do anything but believe themselves to be invincible ki warriors.
A decade after walking away from the art, and I'm still frustrated by this fact. If the ideas were stupid, I wouldn't be annoyed, but the ideas work...