We have started using it in peripherals to the main application, sort of as a POC as well as a learning opportiunity.
It's looking OK, but we only have 1 graphic artist here who is overworked, and without him, WPF apps still look graphically like developer designed apps.
As well as us coders not being graphical, we're largely still building Forms apps in WPF rather than leveraging fully the power of WPF. I'm sure we could do wonders with more resources and more experience, and am looking forwards to doing so.
We are also considering using Silverlight to appease the boss's belief that there is nothing you can do in a forms app that can't be done on the web. It's a dangerous line though, as he might start believing he's right and we were all just complaining about nothing (actually, he already does :) )