Interesting news today that Adobe is releasing the PDF spec to ISO. Andre Charland has some good thoughts which parallel what I think of it. The more open we get with these web technologies the better. (Scoble also has a good overview of PDF if you haven't looked at it in a while).
Now a lot of the spin on this will probably be Adobe vs. Microsoft. Part of that is warranted, and things like this Ars Technica article show how large the issue of openness is looming. I think the idea of XAML replacing HTML is completely ludicrous, but there clearly are two different approaches to the web between Adobe and Microsoft. Adobe took a big step today in moving to make the PDF spec an ISO standard, and in the "war" of document formats, this is significant. It should be applauded and Microsoft should take note.
I also hope to see more opening up by Adobe, and I think we will. We saw some of this with the creation of the Tamarin project. It would be great if these RIA platforms were as open as HTML. Moves like this help contrast Microsoft and Adobe at a time when developers are looking for new ways to build great experiences. I have to think that Adobe looks like a more attractive option to developers coming from an Ajax background, but Microsoft's ASP.NET AJAX and "WPF/E" have shown that some parts of Microsoft believe in cross-platform. The question is how open can they be. Right now, Adobe is leading the movement and I hope they continue pushing the "Open Web" envelope.