The big problem with most of the watch bands for the iPod nano 6G is that they just don't look that nice; we haven't seen many that actually look worthy of wearing in public. Hex's Vision Leather ($50) and Vision Metal ($70) bands are a different story: both use high-quality materials and actually make the nano look like a real leather- or metal-banded watch. The company uses what it calls "Clip-In, Clip Out" functionality, a large hole to insert…