There were two reactions after iSkin’s new Soho case for MacBooks ($60) and MacBook Pros ($65) arrived yesterday: we loved the look, but questioned its practicality. On one hand, iSkin—known first for its rubber iPod cases, second for rubber keyboard covers, and third for audio accessories—has branched out into the leather case business with typical panache. Soho looks and feels beautiful: though it may come across as a simple leather…