That's something that would've caught me out; I didn't find an explanation of the 'informal' class div and its declarations/uses when I was trying it out.
My problem with auto complete is possibly related to a problem I had with username ajax validation; http://weblogs.java.net/blog/bleonard/a
When I make a call to a partial from a controller, instead of rendering the partial, the element (the one which is supposed to wrap the ajax-ified area) renders an entirely new <body> tag (i.e. header, main content etc) within itself. My ajax requests are going through, Firebug shows the browser making the requests. Could it be a problem with authenticity tokens? I know the js libraries are included because the ajax requests work (and they don't work when I comment out the script tags).
I would like to elaborate more but the last message in this thread pretty much sums it up;