Back again with more Xceed questions...
I want to be able to get the string values of the filter row (shown below):
The closest I've gotten is the following:
DataGridCollectionView.ItemProperties[columnIndex].FilterCriterion
Where 'DataGridCollectionView' is the current Xceed datagrid collection view. I have looked up the documentation for 'FilterCriterion', and you can set it to be whatever you want, but I see no obvious 'FilterCriterion.Value.ToString()' method or something similar. Any ideas how to read the values in the filter row of the Xceed data grid?

I got a reply from Xceed support, turns out you can get the filter row content like this:
You can access the FilterRow directly by getting a handle on it through it's Loaded event. For example:
You can then get the content of any FilterCell: