Silverlight for Windows Mobile looks like it's (unfortunately) a good way out, or possibly something that might never see daylight.
Still, there's been a little preview and it looks pretty nifty.
I really, really hope Microsoft deliver it in a form that can run standalone applications (i.e. without having to be deployed from a web server), and with the Silverlight runtime using the full .NET CF 3.5 (I assume) runtime.
I also hope of course that they deliver it within my professional lifetime :)
The UI options for Compact Framework developers are pretty dire: without writing interop code or giving up and just going native, you're limited to something that largely has the visual polish of VB5. It's not pretty.
Silverlight on the other hand gives us the opportunity to create flexible, imaginative and frankly gorgeous UI. It's a shame that it doesn't include the advanced Panel features of WPF (because that would be a handy answer to the horror of resolution and orientation awareness), but some compromises are inevitable. It would still be a huge step forward, and I'd love to see it available as an option for the generality of device applications.
Last but not least, Silverlight+.NET CF+thousands of developers using an application-friendly(-ish) platform enables a good response to the iPhone (if nothing else the iPhone does raise expectations for mobile UI, and we won't be able to get away with more of the same old same old).