These folks are making an annoyingly large amount of news in the PDF space these days.
Hard on the heels of its announcement that Google would begin to OCR and index image-based PDFs came improved support for PDFs in Google's Chrome browser. Now Google's gone and added PDF viewing support to its Gmail application.
My first observations? Gmail's PDF viewer renders the PDF on the server, and shows you a high-quality image of the page rather than the PDF page itself. You get thumbnails, zooming and page-turning buttons, pretty much like Preview in Apple's OS X. You can print the image, or see the PDF convert to simple HTML. Of course, you can download the PDF for the 'real deal'.
The rendering engine is so-so - text is handled fairly well, vector graphics and images less so. Since the 'view' mode simply shows an image of the page, JavaScript, form-fields, bookmarks, links and other features of PDF (and the Reader plugin) aren't available.
Google might consider detecting interactive features in the PDF, then advising users that they are missing features that aren't available in the 'view' mode. I see a few buglets - by default, the page thumbnail highlight appears on the second rather than the initially displayed page - but that's pretty picky.
The PDF love is very welcome, Google. Keep it up. Maybe we'll come up with a wish-list for the Search Santa.