I actually don't like #region in my code. BUT for some reason call me crazy, I would like to have them in my XAML. I would like whole sections to have a #region-like thing and collapse them (e.g. my <Window.CommandBindings>, <Grid.*Definitions>, <Menu>, <Toolbar>, etc..
Does this exist? If not, how about <RegionCollapse>
FYI: This one has been updated to work well with VS 2012 http://visualstudiogallery.msdn.microsoft.com/3c534623-bb05-417f-afc0-c9e26bf0e177
And this VS2012 extension does a nice job of beautifying the XAML so attributes automatically sort and align etc. http://xamlstyler.codeplex.com/documentation
You can add comments to the XAML file using SSI formatting:
This at least gives you some sort of "header" if you use the built-in XML collapse.