Mui 3.8 works fine here 2 on OS3.9 BB2 and if you are a gfx card user like me do not forget to install visual- prefs,reqattack,birdie,deptmenu,caboom and
magic menu to let your workbench look great :-D
For some good skins to use for Mui,birdie etc.. go to:
http://www.grsites.com/textures/blgr001.shtmlyou can even manipulate some aspects such as color and brightness trough the site.
Before i forget your user-startup should be like this:
Assign MUI: "YOUR boot partition:MUI"
Assign LIBS: "MUI:Libs" ADD
Assign LOCALE: "MUI:Locale" ADD
it is a lot shorter then what castellen posted.
And make sure you have mui version 3.8