That's neat. I played around with it a little bit, was able to produce f(x)=1/x, but not F'(x)=1/x, the graph of the first derivative.
Here's a Google blog post (I think the original) that shows some public data related graphs and video content of the features and controls associated with the graph.
And just for mud-slinging, but informative (in links and useful info, I must warn - cluttered as my workbench, this site) drumroll please... Wolfram Alpha and Google Graphs compared.
Thanks for the interesting post! Glad I found it.
very cool, i already use google search for quick math & spelling. good to see them include more funtionality Wolfram Alpha has.