Trebuchet is a 100% TCL cross-platform GUI MUD client, designed to be powerful and extensible, yet easy to use. This client also has support for advanced features, such as SSL encryption, and allowing the server to request custom GUI dialogs.
Trebuchet is exceedingly good at what I use it for, connecting to FurryMuck, it could so with more 'live' troubleshooting.
Over the last eleven years, I have been exceedingly happy with how easy Trebuchet is to use under OSX ... and even back under OS9. ^_^