Although Flot is easy to use, it is also advanced enough to be suitable for Web 2.0 data mining/business intelligence purposes which is its original application.
Flot will certainly replace any server-side graphics creation which require lots of memory usage. There are many interesting examples that you might check to see the capabilities of this great library. Flot uses Canvas to draw graphics on the fly, it requires ExCanvas library to work on Internet Explorer. Released under MIT License.