MU in comparison to regular WP has somelimited functions. This is mostly becuase to have some functions in WP the user needs to be able to tweak their own code, upload plugins, themes etc.
But out of the box it is otherwise it works the same. Theme developement and design is basically the same, but in order to add themes (ftp) you would need to give someone ftp access to your site and it would be done in that fashion. Alot of plugins work, and can be activated by each blog owner, or implemented sitewide, usually with a little tweaking to the code.
At time MU is a little buggy, but some of the bugs are there becuase it does require php, mysql, and interpretive dance experience to maintain. Not alot of any of those but they are handy. Some of the bugs come becuase almost every server that it is installed on is different, so each install needs to be tweaked to match the server.