The prong adaptor set is the smartest and cheapest option for around-the-world travel. You can get a 2-prong adaptor at travel stores (e.g. REI, $3) and plug your U.S. prongs into the skinny, tiny prong adaptor (ultra-cheap!)... you can look around the airport on arrival and buy whatever is there... or you can search for an Apple store on arrival and buy a iPod power block, remove the prongs and fit those onto your Mac power block. The Mac power block does handle European voltages, though.