pdf on xoom
While playing with the Xoom at a Best Buy I downloaded a pdf viewer (free official Adobe one) and a couple of pdfs and they looked great. They scaled to the full screen perfectly and all the reader settings (single page view; view as long scrolling document, etc) seemed to work fine. Pinch and zoom also worked.
As a teacher, pdf support is essential for any tablet I consider. I tried the Kindle DX for a while. It was okay, but I think I'd rather have the speed of scrolling on a tablet versus the readability, and slowness, of e-ink.