Moshi's new Muse ($30) illustrates the difference between merely releasing an iPad-sized sleeve case and actually designing one that really looks and feels great. Over the past seven or so years, Moshi became known for its excellent use of microfiber fabrics in iPod and iPhone pouches such as iPouch, and Muse takes the material to another level, with tailoring, stitching, and thickness that are akin to a high-quality sofa rather than a typical bag,…