Worked perfect, just needed to change == DateTime.MinValue to check for my value and have the Text blank instead of "Null", which isn't really "user-friendly ;).  Thanks again for your excellent support!

    public class MyCreationFilter : IUIElementCreationFilter
    {
        #region IUIElementCreationFilter Members

        void IUIElementCreationFilter.AfterCreateChildElements(UIElement parent)
        {
            // Do nothing
        }

        bool IUIElementCreationFilter.BeforeCreateChildElements(UIElement parent)
        {
            // Watch for a TextUIElement
            TextUIElement textUIElement = parent as TextUIElement;
            if (textUIElement != null)
            {
                // Is this TextUIElement in a grid cell?
                // Is it a DateTime column?
                // Is the value DateTime.MinValue
                UltraGridCell cell = textUIElement.GetContext(typeof(UltraGridCell)) as UltraGridCell;
                if (cell != null && 
                    cell.Column.DataType.IsAssignableFrom(typeof(DateTime)) &&
                    cell.Value is DateTime &&
                    (DateTime)cell.Value == DateTime.MinValue)
                {
                    // Show some user-friendly text.
                    textUIElement.Text = "Null";
                }
            }

            return false;
        }

        #endregion
    }

Hiding the cell will not work as we are styling the grids and a big empty space will not look right.

I've done some CreationFilter stuff before, but not connecting how I would use it here.  If you could give me a quick example to get me started that would be great.