Slider cases -- two-piece plastic shells that separate near the bottom of Apple's devices -- have become popular over the last few years, and Incipio's EDGE for iPhone 4 ($30) is its latest version -- a matte rubber-finished hard plastic shell that comes with a piece of screen film, a cleaning cloth and applicator card. The camera hole on the back is black-lined regardless of the color of the case to prevent flash problems, and holes provide access…
