My favorite was the "Xylo" case, cause even though the other cases were nice, they made the phone a little bulky, possible making you feel like you were caring around a treo or blackberry. But I understood that the reason they were bulky/big was to provide adequate protection to the iPhone
Maybe its just me, but I think that when an electronic is as stylish as the iPhone you shouldnt cover it up. When I get an iPhone im gonna buy an Agent 18 case, with a Sheildzone/ bodyguardz protector