Thunderbolt is getting closer to becoming a practical standard. Plenty of expensive, stationary desktop units were announced before Buffalo debuted the MiniStation Thunderbolt Portable HDD ($200-$250), the first bus-powered portable Thunderbolt hard drive we’ve come across. Now instead of having to invest a few hundred bucks into several terabytes worth of storage, the average Mac user can get 500GB or 1TB in a portable package at a reasonable…