Are you encouraging people to simply test WebM or actually use it?
The VP8 and WebM specifications as released on May 19th, 2010 are final and we encourage everyone to use them for developing applications. Google, Mozilla and Opera are all adding WebM support to their browsers and all videos that are 720p or larger uploaded to YouTube after May 19th will be be encoded in WebM as part of its HTML5 experiment. The WebM/VP8 source code and content creation tools are a Developer Preview with room for further improvement of the code. We encourage the community to help us complete the work items on our roadmap.