I haven't actually tried d3.js. I encountered significant speed issues when using Raphael (even when panning a graph), and I assumed that was more of an SVG problem than a Raphael problem. Maybe I shouldn't assume so much, but I didn't think d3.js would be suited to showing graphs with multiple data sets with potentially ten thousand points (or more, there's a data point for each second, and it's not uncommon to be riding for more than three hours) each.

See this[0] page for an example of a d3.js graph with ~600,000 total data points.

[0] http://hn.metamx.com/