Is there a way to get rid of the 4 tabs? How about split the description-field into 2 fields: type and description. The sorting by type would have the same functionality as those tabs. What is more interessting IMHO is a textfield for filtering the data below.

What would be cool is a buttom right to Copy to clipboard, which generates a QR-code from the actual adress. I think there is a library for qrcodes around: http://fukuchi.org/works/qrencode/index.en.html

Another idea: In the send-dialog: When sending to an unknown address, can the user type in a string which is then included in the adressbook with the address?