Personally it is so much easier for me to try out new ideas on Plan9 than it is on Linux or anywhere else.
same here, with the small addition that p9p relieves a lot of the prototyping burdain on Linux too. we got a small system written in p9p (so it runs on Plan 9 too), got it to be reasonably stable, evaluated (even by end users) it and now it's off to be rewritten in Linux' native tongue. way less painful than it could otherwise have been.
