Yeah Microsoft benchmarks sucks!
That's what I thought when viewing the video. Why would anybody look at Microsoft benchmarks desinged for IE.
With Mozilla demo running on Chrome Beta I get 35fps with 1000 fishes and still it's much smoother than the Microsoft benchmark with 10 or 25 fishes.
I've found some good demos of Stage3D. They are created with Minko a 3D framework for the web. Aerys company behind that technology already works on Minko 2 which supposedly will bring big performance improvements. The game they developed with it runs much better than Epic Citadel but it's also even less impressive graphically The Mirage.