Doesn't load for me, and I don't think the intended use as gif replacement is 50 meg trailers inline and auto-loaded.
Plays just fine on my 9 year old Pentium laptop; you trying to watch on a tablet or something? More efficient gifs are fun, but it's certainly not the primary intended function of webm. I'm personally more excited to have found a simple way to display and share 60 fps content online without dealing with slow-ass Flash players and 30 fps limits.