Right now at least on Windows 7/FF8 the UI of the "Add item by identifier" is curiously unresponsive. There is no submit button and the cursor keeps blinking after hitting Enter, meaning there is no feedback whatsoever that you have even submitted the identifier let alone that it is now being processed.

Proposal: The UI should clearly distinguish between "receiving user input" and "processing user input". Simply greying out the field after submission would be enough.