This was inspired by a question I asked recently regarding design time behaviour in my WPF app. (Can't databind at design time in WPF using MVVM - ViewModel property never gets called)
The net result of that is that my design time DataContext/ViewModel works perfectly in Blend, but doesn't show up in Visual Studio 2008. I've decided not to look further into it as Blend support is all I really need, but this surprised me as I had been working under the assumption that Blend and VS would have similar if not identical WPF designers.
So what are the differences? Any other gotchas anyone is aware of? All info welcomed :)
In short, WPF matured after VS 2008, so the designer is pretty much crap since it went in very late in the development cycle for Visual Studio.
In VS 2010 however, the designer is much improved (as well as app WPF stuff in general...a lot of the VS 2010 components are WPF themselves), but I would stick with Blend for now. I personally use Blend for the design, Visual Studio for the code.
Coming up shortly with VS 2010/WPF 4: