I am plotting about 500 items on the map and everything works fine until I zoom in or out. When this happens the CPU goes to 100% for 10 or so seconds and then things work again until the next zoom.
I used ANTS and found that all the slowness is from the method Telerik.Windows.Controls.Map.FileCacheBase.SaveFilesThread().
I also noticed this xaml error which is not from me:
System.Windows.Data Error: 25 : Both 'ContentTemplate' and 'ContentTemplateSelector' are set; 'ContentTemplateSelector' will be ignored. ContentPresenter:'ContentPresenter' (Name='')