It's been a while coming, but I've finally gotten a public beta release of my MU* client out for testing. It's called Potato (don't ask me why;) and you can find it at http://potato.talvo.com. It's a graphical client, and runs on Windows and Linux.
It's completely usable, though being a beta release it is missing a couple of things here and there (mostly in terms of documentation and missing menu entries for accessing the features that are present) -- the main features are documented on the website. A couple of minor bugs and missing features have already popped up since I released it, though (many thanks to the people who've already tried it and left feedback!), but I'm working on getting those fixed ASAP. Any comments, suggestions or criticisms are very much appreciated, either on here, by email, or via the ticket code on the website. Hopefully you'll find it useful. :)