p.s. you can see our sample client-side apps here: http://vimeo.com/groups/fabric/videos and play with them at http://demos.fabric-engine.com

You can how we've extended Fabric to include existing C++ libraries - great for custom data types, streaming data etc

It is not really a consumer web technology - we're acutely aware of the plug-in friction/antipathy. However - if you want HPC in the browser, this is one of the only ways to do it.