FWIW, in 11.1.20111.2054, a grid's persisted settings seem to take precedence over what's in XAML (presumably earlier builds too).  I noticed this today when I added a GroupByItemTemplate to one of my columns and it didn't seem to work.  After clearing the isolated storage area for my PC, I re-ran the app and everything of course worked as expected.  Unfortunately, this makes for a very messy deployment - i.e. my app is already in use - so to get my new group by template to show up, I'll have to contact all users and tell them how to clear their isolated storage and also pass on the bad news that the setting preferences for all their grids will need to be redone.

I realize I could add code to my app to clear the storage and perhaps even merge in their old settings but this seems like a fairly major design flaw.  I love the fact that the grid can persist/restore all its settings in so few lines of code, but not being able to change my XAML and have those changes show up automatically after the grid has been restored from persistence makes it fairly useless except for one and done type apps where the grid's XAML will never be changed over the life of the application.

Thoughts???