One of the fundamental issues with MU*ing has to do with getting everyone on the same page. In short - it's impossible.
People want different experiences. They have different levels of familiarity with the source material and are after different things. Their expectations, thus, are also different.
Take a Lord of the Rings setting. I might go in as a big Tolkien nerd and expect something beautiful and lyrical. Others might see it as a D&D adventure; they want to slice and dice some Orcs. For some it might be that they want it to be more L&L, play some politics, see if Gondor will finally atone for Westfold.
This isn't made any easier for the fact there isn't just one Storyteller/GM/DM around but several and they will also offer different points of view based on their own preferences.
In my opinion the true answer is this: For small sub-groups of people there is potential for such a thing as a shared desired experience. For larger groups expectations need to be managed and compromises made.
In other words - I'd advise folks to find and surround themselves with people who want about the same stuff they do as much as possible. When they venture outside of that circle though their results may vary - sometimes pleasantly.
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