In canvas's defense, canvas and SVG/VML are different tools for different jobs.

For a charting library, you should absolutely use SVG/VML instead of canvas. You don't need the bitmap properties of canvas, canvas doesn't scale well and you can't transform paths like you can with SVG/VML (without redrawing the whole thing).

To do face recognition, bitmap image gymnastics or build an online Photoshop tool, SVG/VML isn't going to cut it though --- you need canvas. Try making a spray paint tool with SVG/VML. Ouch! Using a canvas that's almost trivial.

Good tutorial on using Raphael though. It's a great library.