The charts component of M2M2 (when viewing a data point or watch list) works very smoothly and I'm sure a lot of effort has been put into making it work this way.
I use it all the time but compared to tools like DGLux, librato, etc. it feels... very dated!
However, perhaps the developers can consider switching to something like Rickshaw JS graphs:
It's built on the popular and powerful D3JS library: http://d3js.org/
But it is very lightweight and simple to implement.
It can also update the graph values via AJAX or JSON/P which would be really nice in Mango, plus it can do things like tooltips.
Here are some examples: