Do you really like the native Windows dialog that much more than the (IMO) more powerful GTK dialogs?
OMG Yes! The GTK dialogs ares too limiting. I can't do file management tasks from the GTK (if I have a naming conflict I'll delete, move, or rename another file before saving... why switch to another app or terminal to do that when it's right there?), the views/sorting is better in Windows, breadcrumb navigation SUCKS when you're working on the same file in side-by-side directories/branches, etc. It's actually one of the few refreshing things when I'm using the Windows laptop... and I would even go as far to say the Windows dialog should be default on the windows builds!
-Tim