Satellite radio hasn't been around that long, but we've had portable tuners for years. Why has it taken DirecTV so long to create Sat-Go, the world's first portable satellite-TV receiver? Lots of reasons, I'm sure, chief among them, "Why would you want one?" But now that I've had a chance to play with Sat-Go, the "why" feels irrelevant -- I just want one. This is one cool gadget.