I've tried both Zagg IS and bestskinsever. From experience, Zagg has the prettiest packaging, but I've had the most quality experience with bestskinsever. Old 5G iPod (black) still has bestskinever skin I originally installed. Zagg IS "orange-peeled" away from my iPhone 3G in less than a year.
Both great skins, but you should already know what I have on my iPhone 4. 😉
-C
Sent from my iPhone 4