A slick UI without a doubt, but most (if not all?) of that is provided by the OS itself, and as far as interfaces go not having a dual pane local/remote view makes it very hard to use, not to mention lots buggy of behavior in other areas.

The biggest problem though is that the file transfer bit ... you know, the part which actually makes the app of any use ... it's flaky as hell. "Solid Connections" ? Nope.