I have made the experience that editing large XAML files is extremly faster when doing it in the standard XML text editor instead of the the split-screen cider XAML editor with the design view. This is also true when I have the "Always open documents in full XAML view" option enabled. Allthough it gets a little better when this option is enabled, I still experience lags and performance issues. Not so with the standard XML text editor. It always works like a breeze there.
Now I am wondering if there is any disatvantage of using the XMl texteditor. Everything still seems to work such as intellisense, autocompletion, error highlighting. The only thing that is missing is the codebehind functionality (navigate to eventhandler, etc.) but I don't need that anyway because due to MVVM I never have codebehind.