Rarely does a week end these days with an unexpected and happy surprise, but Speck has delivered one in the form of CandyShell for the iPad, a sequel to its award-winning series of cases for the iPhone 3G/3GS and iPod touch. Harkening back to the olden days of iPod accessory design, when Speck innovated one of the very first Apple Dock-compatible cases, CandyShell is the first case we've seen with a flap on the bottom that opens up to work with…