I'm a big fan of WinSCP when I'm using Windows, and I think Cyberduck could take some of WinSCP's features and be all the better. I've already put in my vote for a two-paned interface. I'll add to the list:
Synchronized browsing. Navigating to a remote directory also navigates the local directory, and vice versa (goes hand-in-hand with a two-paned interface, of course
Compare directories. This is distinct from "synchronize," because it simply highlights the differences between the local and remote directory. This is a convenient non-destructive action that helps see changes.
Also in line the the idea of a two-paned interface, the option to save the local directory with your bookmark. Cyberduck has an option for saving a "download folder," of course, but this doesn't do much good if you're transferring files in the web development process.
I'm a relatively new Cyberduck user, so forgive me if I'm unaware of existing functionality as I've described it. Thanks for listening![/list][/url]
Enhancements to take from WinSCP
I have opened http://trac.cyberduck.ch/ticket/1148