Charles Petzold hit a homerun! His ‘Writing More Efficient ItemsControls‘ article in the March 2009 issue of MSDN Magazine is the first treatment I’ve ever seen on how to analyze and address performance issues related to the use of DataTemplates and ItemsControls. He uses empirical evidence to identify performance issues related to a DataTemplate, and shows various ways to improve them.
After reading the article, I am definitely going to go through some templates I’ve created and reassess them. If you are interested in keeping your WPF applications running quickly, I suggest you check it out.