I'm all for Federalism but I think it really depends what country you live in. Countries that have a strong history of diverse regions with their own independent histories like the U.S., Canada, Germany, Russia, etc. are best able to realize all the benefits of Federalism, but countries with a history of a strong central authority may not be as able to. Poland or France both have powerful centripital historical traditions, while Germany or the U.S. have powerful centrifugal traditions.
When my wife and I went back to Poland last September, we found ourselves wandering across unfamiliar borders because the government had drastically reorganized the wojewodstwo (provincial) borders, eliminating dozens of wojewodstwy. Can you imagine Washington deciding to consolidate the 50 states into 15? That's the issue, that in Poland power derives from Warsaw while in the U.S. power derives from a complex contractual agreement between sovereign states and a central authority. In short, in Poland Warsaw makes the states but in the U.S. the states make Washington. Federalism is very successful but I'm not so sure countries like France or Poland would be very good at finding that balance between local and national authority that is critical in Federalism. The Russians have the best case for becoming a Federalist state with their vast and disparate territories and they are one - in name, at least. In reality, Russia is still one of the most powerfully-centralized states. While there has been progress, Moscow just doesn't seem able to let go of its authority.
So maybe history plays a critical factor in the success for Federal states...