Thanks. We still need to clean up the code a bit, and should be publishing more docs on how the thing is structured this week, so keep your eye on our github repo.
we opted for canvas as it gives us better visualisation capabilities in the future. we could easily provide searching with canvas by overriding ctrl+f.
In general I like SVG because it doesn't try to hide the data it's displaying, unlike flash/canvas. Although I now remember seeing a hybrid div/canvas implementation which buys you best of both worlds albeit at some added complexity.