The big announcement this year was the new Windows Azure Cloud service that I have mixed feelings about. I think it could be useful for small businesses and startups to offload the maintenance of datacenters to Microsoft (and having them deal with scaling issues), but I doubt enterprises would like to have microsoft handle all their presious data.
They also showed alot of the upcoming Windows 7, which in my (and many other people I talked to during the week) opinion is more like "Vista as it was supposed to be" than a radically new version of Windows. They finally have the new search stuff in, including support for virtual folders to replace the "My Documents" / "My Photos" stuff that have been around since the '95 days. In Win7, you have "libraries" instead, which contains an aggregated view of several folders, so for example the "Music Library" could contain all files in $userhome/my music, d:\music, e:\other-music and still be maintained from what to the user seems like a single location. Nothing radically new (the idea has floated around the OSS community for some time) but I think it's nice nontheless. If nothing else, it makes it easier to separate the user data (docs, music, videos, etc) from the system data (os files, program files etc), something which has been possible but quite hard before in windows. (In Linux, of course, you just mount /home from a separate partition and be done with it)
The big thing about win7 in my opinion will be the addition of multi touch devices as a first class input device. This means that if you have a multi touch screen, like the newer displays from HP) they will seemlessly work with windows 7. In the open source world, multi pointer x should be able to provide the same kind of built-in functionality and I hope distributors will begin to incorporate ones it matures a bit more. I'm definitely keeping my eye on that project.
I also got a chance to talk to the Novell people at PDC. Aaron Bockover from the Banshee project was there and he showed some of the cool stuff he's been working on for banshee, including the d-bus interfaces and port to OSX. I asked him about what he thought of adding full WPF support to mono and he gave the "we've talked about it, we're interested in it, but we don't have any plans to do it yet" answer. Unfortunately Miguel was never around the booth when I was there so I never got the chance to ask him directly about it. I did go to see his talk about Mono and .NET and it was one of the best talks of the entire week (and that says alot, since there were many interesting sessions there!). He showed the new C# command prompt thing which was received with apploads and laughter since just a few days before, Anders Hejlsberg (chief architect for c#) showed something very similar but that is just in pre-planning and won't be shipped for several years (if at all). Nice to see OSS is taking the lead here.
Miguel also talked about the move to mono done by many game vendors and how the open model of mono enables them to use it in ways that simply wouldn't be possible using microsoft's closed license model. Game logic is traditionally written in slow scripting languages like LUA to make it easier, but it also makes it less performant. Using c# instead seems to provide a very good middle ground for these kind of things.
Update: direkt link to miguel's talk.(wmv download. Also available as mp4 download)
Update2: fixed mp4 link