Adobe announced Acrobat 7 today. It seems to be mostly improved presentation and value. Apparently people with the Professional version will be able to create a PDF with commenting functions enabled for people who have the latest version of the Reader. And Elements might be available in quantities lower than 1000. The forms design kit will be included so more people will begin to think about the server software.
Already some people think it could still be cheaper.
Macromedia have something to offer with Contribute. This is priced for volume in a way that education can afford. Contribute allows commenting and also creation of PDF or Flash Paper. Flash Paper loads very fast assuming you already have Flash working. The claim is that Adobe Reader 7 will load quickly anyway. Something to come back to.