It connects to some services that no other client can:
http://cyberduck.ch/With an easy to use interface, connect to FTP (File Transfer Protocol), FTP/TLS (FTP secured over SSL/TLS), SFTP (SSH Secure File Transfer), WebDAV (Web-based Distributed Authoring and Versioning), Amazon S3, Google Storage, Google Docs, Windows Azure and Rackspace Cloud Files. Works with emerging open cloud software from Eucalyptus and OpenStack.
Update: Still untested. Installed, copied contents of Program Files, but program wouldn't start (looks like an XP SP2 incompatibility).
Update2: Doesn't look like its going to happen.
Update3: Someone submitted a feature request, but doesn't look good.