It should be noted it worked, as long as Tito, also known as the last Hapsburg was in charge. I'd recommend watching Death of Yugoslavia on Youtube, it shows perfectly how step by step, creeping nationalism managed to destroy the experiment. Neither I, nor Betonov are saying that things were perfect or that there were no cultural tensions under Tito. While they were usually "taken care of" by Tito and the Party by any means necessary (which I cannot condone), the general feeling was as described by Betonov. Politicians, working to advance their own position, used the genie (or better yet, Pandora's box) of nationalism to get what they wanted. That is also what they got; war, destruction and suffering for the people and fat pockets or power (or both) for themselves.
Even today, there are still buildings in the Croatian littoral that stand as a silent reminder of what happened there. No owners and no-body to tear them down. Old shelled shells of a, in the end, failed experiment. While there was never any Yugoslav nation or culture that developed naturally (outside of imposed centralism in the later years and in the Kingdom of Yugoslavia), people lived and worked together. And that is what a successful multicultural "experiment" looks like (although the question is far more complex than my sentence shows and could fill pages and pages).
An extra:
Here's our boys!