Heh, to each his own. I've always held that the Java widgets are some of the ugliest I've seen since Motif, but Claudio compares them favorably against Qt.
...tellico is QT and thus ugly as hell (not as important, but not pleasant to work with).
By contrast, JabRef has a very clean interface and the search is fine for my needs (regular expressions). You can even change the look and make it look it like a GTk+ application.
I didn't know about the Gtk+ theme. I'll have to figure out if I have that available somewhere on my system.