Many people don't like typing very much. Without doubt MUDs are attract more people with higher education, since most of them do have minimal typing and computer skills. Better clients with buttons or menus for commands may help overcoming this problem.
The biggest problem in traditional MUDs were in our opinion the interfaces to large structured or unstructured text. Conceived a long the same lines as ``Unix-style man pages'' or files sitting in some directory, larger text was hard to read while having simultaneous discussion. Information was sometimes hard to find and most important: the MOO was cut from the rest of the world. A few in-MOO solutions were to build ``books'', ``tutorial rooms'', menu-based ``news-papers'' and such which already provided users with friendlier interfaces. Also, gopher and www slates allowed to access those popular Internet services via a simple line browser. Despite their usefulness, those tools still put unnecessary strain on todays average professional users (who do have a networked computer on their desk). The emerging WWW-MOO interfaces do handle part of that problem very well. The user can concentrate on communication in the MOO client and on reading and inspecting objects via the WWW client.
Other problems are related to the fact that MOOs were designed for enthusiasts and not for casual users. This is no issue for social MUDs, but it is for ``serious MUDs'' who do not want to exclude people by their ability or will to cope with the help system and remembering of dozens of commands. One big problem is editing. Todays users certainly don't want to play around with the moo note editor. This is a problem that could be easily solved via better clients. Indeed, the MOO allows shipping editing tasks to other applications in principle, but so far none of the most popular clients seem to take advantage of that. Also, many features should have a standard ``menu-based'' interface. Although menus are slower for experienced users, casual users can't remember all the commands needed e.g. for news-groups (mail) manipulation and don't want to read the documentation all the time. Sequences like ``help + help @mail + @subscribe + @subscribed + @mail on *general + help @mail + @mail 1-$ on *general + @read 2'' not mentionning all the commands missed or mistyped are just too long. Even Unix's good old rn or mail did better than that.