@QuickC: please note that apart form the previous 2 posts to this one. all the posts in this thread are over 2 years old.
Thread necromancy be damned, I'm going to make another of my trademark WPF-bashing posts.
Today I ran a little program from Codeplex that provides additional services to iTunes. It provides a very simple UI comprised of three tabs with a bunch of textboxes on and not much more.
Something like this could be done with WinForms or GTK# and load instantaneously and look good (with judicious styling and 'System' FlatStyle). But no, this was a WPF application. It takes 3 seconds to load every single time (it took 7 seconds to load the first time) and this is on a Core i5. The text rendering is dodgy (even though ClearType is enabled system-wide). The controls and widgets don't look right when compared side-by-side with their native equivalents. Opening one of the other tabs in the application causes it to freeze temporarily whilst it initialises. And it features a scoop of "because WPF lets me" styling that looks atrocious.
The theory behind WPF could have been something special, but Microsoft mismanaged it and so we're left with this.
And I'll remind everyone of one, key, fact:
There does not exist a single non-Microsoft WPF application that doesn't want to make me tear my eyeballs out. And many first-party WPF applications are still highly suspect.