Re: Injecting the good stuff via jQuery = :[
It's certainly possible to apply the behavior via jQuery, as the css3pie.com homepage does exactly that for the demo. Try using the syntax:
That said, applying the behavior this way has performance implications, namely that you won't get any CSS3 styles applied until after jQuery and any other scripts have fully loaded and the documentready event has fired. This is one of the big advantages of using HTC-via-CSS rather than JS as the wrapper for PIE: it can be downloaded asynchronously and can be applied right away, often before any of the page has been rendered, so you don't get any flash of unstyled elements.