I've been playing around (http://yield.io) with Flot, which uses canvas and rendering speed seems pretty good, but resizing gets a bit wonky when there are multiple canvas elements on a page.
Yeah, we started with Flotr2...too many graphs on a page (with thousands of datapoints per graph) brings Chrome to its knees, even with auto margins and whatnot turned off.
@angersock That's a good point on the number of points. If I downsampled the yield history to monthly yields, that would probably help the performance.
EDIT: Very clean site! I like your style. :)