I implemented something similar with Dygraphs. The "killer feature" with that was instantly zooming to any detail (e.g. from 1 year to a time window of 10 milliseconds). The client would instantly show the level of detail possible with the current dataset, and fetch the detailed datapoints in around 100-200 ms.

Anyway, I believe zooming to be a very typical feature for time-series (e.g. Google Finance supports that), so I hope this library has good support for it too.