There's an article in this month's MSDN magazine on building Office-based solutions using VSTO with WPF, WCF and LINQ. The point of the article is to affirm that all these disparate technologies do indeed work well together, and that the design-time experience of building such a solution is suitably RAD. The article is also online here.
Right now, the accompanying sample code download is unfortunately an early version that doesn't match the article (thanks to Andy Cheung for pointing this out). The posted version of the code also doesn't work with the final release version of VS 2008. I'm working with the gentle folks at MSDN to fix this as soon as possible. Meanwhile, I've attached an updated version of the code to this post – this version does work with VS 2008 RTM.