Ask HN: Web Charting Packages

Ok, the longest ongoing open project at work is finding a decent charting package. None of them solve all of our problems.

1) Scale - we have ALOT of data points, potentially 10's of millions. It would be nice if the package dealt with this in an intelligent manner.

2)Interactivity - We don't want just a flat image that isn't easy to interact with.

3)Looks professional

4) Chart Types

The solutions we've found are in four main categories: Java based, PHP based, Flex based, and Javascript based.

Java, PHP: We've found them to scale well, but look not as clean/professional as we like, and are not interactive. Most chart types. Ex, JFreeChart

Flex: Look nicer then the Java/PHP charts, do not scale as well, though they have excellent interactivity.

Javascript: Do not scale well, best interactivity, nicest looking charts. Much newer packages then other types, many still in development and do not have all the chart types we need. Ex, flot, visualize

What packages do you have experience with and why do you love/hate them? Would they fit the needs outlined above? Thanks!