Raphael.js definitely rocks. I've finished a little coding project (it's a visualisation of an algorithm; didn't release it yet, though) and it was really a pleasure to work with the framework. You can do really a lot of cool things with it. The demos on the Raphael.js page are also quite impressive, and run pretty fluid on almost every browser (my project runs pretty fast in Chrome, but loses it a little bit in IE, perhaps because of the layer added by excanvas). That said, I have to admit that I love Raphael.js, too. It's surely not the last time that I've worked with it.