Where is the bottleneck in the JS version? The major browsers are coming close to releasing GPU-accelerated canvas. You might just be a bit early...
For example: the JS version is choppy, but usable at 2560x1600 in Chrome on a PhenomIIx4. However, if I switch to the Chrome Canary build (http://tools.google.com/dlpage/chromesxs) with --enable-accelerated-2d-canvas it is significantly less choppy. At 1920x1200 it is downright snappy.
The bottleneck is mainly in rendering. Plus I actually took a lot of 'blur n zoom' effects out already (which is where the silverlight version really excels I think). I'll put them back in and retry (it's a kind of blend like anim)
I'll check out the 2d canvas - thanks for that. Ironically the IE 9 works very well too, although that group of users always seem to have Silverlight already :)
With traffic non-existent to the site it might just be too early, or perhaps some best suited as a native iOS app instead.
For example: the JS version is choppy, but usable at 2560x1600 in Chrome on a PhenomIIx4. However, if I switch to the Chrome Canary build (http://tools.google.com/dlpage/chromesxs) with --enable-accelerated-2d-canvas it is significantly less choppy. At 1920x1200 it is downright snappy.