I've been experimenting with Visual Studio Orcas (beta 1) lately, to see if it's any better, particularly in 2 places where I'm having pain writing WPF apps in VS 2005:

1. Showing XAML files in design view, if they contain UserControls, or represent a custom class that derives from a WPF control type.
2. Describing the ACTUAL error when there's a problem loading a XAML file. (the dreaded "Cannot create instance of XYZ defined in assembly ABC... blah.xaml, line 2, position 5". Of course, that location in the file is nowhere near the code causing error (it's usually the first namespace declaration for the outermost element in the XAML file).
   

I'm happy to report, that with Orcas, both problems are fixed (at least to some extent)!

1. After wading through seemingly tighter, more picky error reporting by the Orcas designer, I have been able to view my UserControl and custom class derived XAML files in deisgner mode!!
2. I just ran into the error in XAML file exception in VS05, loaded up the same solution in Orcas, and the exception there pinpointed the line (and character!) where the problem was (still a little funny - the error was in the code-behind for a custom class, failing on a DependencyProperty.Register method [bad parameter type FrameworkPropertyMetadata instead of UIPropertyMetadata?] -- so the error shows up in the XAML file that contains that failing class).