Orcas Beta 2 is here, and it includes a go-live license. I plan a switch over (plus a clean reinstall of Vista) by the end of this month. I do prefer to use the latest tools to keep on top of technology, and, despite the installation being a distraction from my current work, I do feel rejuvenated by a sense of progress and change of scenery.
I have been developing in Orcas Beta 1 for about a month now, but haven't been using any of the new compiler features and libraries. Both Refactor Pro and Resharper have latest versions that will run on Orcas, though I don't think Resharper 3.0 supports the new language syntax yet. With the go-live license, it might even be possible to use the LINQ APIs even though the product has RTMed, but I'll wait.
It is hard for me to recall a specific benefit of using Orcas, but it is very stable and doesn't require Administrator privileges to run. Most of the benefits from using the IDE come are related to .NET 3.0/3.5 (which include WPF and LINQ).
I am not planning on using WPF in the near term, but it is something I am currently looking into the future. And if I were, it would initially be from inside a WinForms application using its interoperability features. I also don't see a compelling reason now to use it. I have seen a couple reports that WPF is not ready for prime time use, Rod Paddock, Eric Sink and Lhotka. I have seen ribbon and other components from ActiproSoftware, DevComponents and Infragistics, but the component libraries are still minimalistic and not fully developed. The runtime, required for Windows XP, also adds 2.8 Mbs to my setup package, and forecloses my ability to run in Windows 2000 (though, I must admit, I can't guarantee NStatic even runs in 2000 in its present state).