Though we've seen more interesting designs from the company in the past, XtremeMac's latest iPhone 4 cases aren't bad -- they're just me-too, and represent so many variations on the same general theme that they're hard to get excited about. There's the competent enough single-piece translucent clear Microshield for iPhone 4 ($20), and the more interesting Microshield Accent ($25), which has a soft Bumper-like border to cover the edge of the iPhone…