Perhaps it's just a problem with the documentation but it took me a while to figure out that setting the Format field on a PropertyGridItem does not affect the display unless you re-assign the value of the item.  This seems odd as I need to create the item with it's value, then assign the format and then re-assign the value.  Wouldn't it make sense to update the field when the format value is changed? 

Another minor issue is ,when using ATL, the Constraints add method doesn't work properly unless you specify the index.  If you leave off the optional index parameter assigning an enum value of anything other than 0 makes the field blank.