Pixastic works by utilizing the HTML5 Canvas element which provides access to raw pixel data, thereby opening up for more advanced image effects. This is where the "experimental" part comes into play. Canvas is only supported by some browsers and unfortunately Internet Explorer is not one of them. It is however well supported in both Firefox and Opera and proper support is hopefully coming for Safari soon (Safari currently only works with the WebKit nightly builds). A few of the effects have been simulated in IE using the age old proprietary filters. While these filters are much faster than their Canvas friends, they are few and limited. Hopefully we will one day have real Canvas on IE as well.
The ability to manipulate image data directly is one of the more compelling features of the next generation of web browsers. I'm looking forward to the day when I can cut and paste an image directly into a blog post, adjust its color and crop it, all without jumping back and forth to an image editor.
Check the Pixastic site for more details on the supported browsers and available filters. There's also a small snippet of code that shows you how to use Pixastic with jQuery.