First of all this is a great plugin, thanks for creating it. I love the ease of use, it's nearly perfect. The only thing I'm missing at this moment is a disable button for the duplicator in the custom field creator.
E.g. I'm using WCK and the duplicator function to create a restaurant menu. It would be very handy if an item goes out of stock, I could just click the disable button for that item, so it doesn't show up anymore. When it's back in stock I click enable to show it again.
Doing it the old way by deleting an entry, an readding it works of course, but this seem handier to me. And I'm pretty sure it could be used in many environments that custom fields are used for. :)