Along with a handful of simple updates to older cases, Speck has just shipped us a new version of its PixelSkin HD Wrap ($50) for the third-generation iPad. The previous edition was one of the best rated cases for the iPad 2, earning a high recommendation when we reviewed it last April. This revised version is made of the same rubber, but has some real differences when it comes to the cover. It's now divided into four sections rather than three, making…