One thing they've clearly made an effort to do is make work as the same codebase across versions, it's beautiful bringing up their linux client as an example of good installation.

however, one of the primary things I think they could implement that would help more is implementing the decidely windows-aimed feature of Napster where clicking the X in the upper right actually causes it to minimize to the system tray instead of quitting. I know it sounds sneaky, but users who don't realize that LimeWire is still backgrounded is a good way of extending the fabric.