I use an Incase Snap on my iphone4 and carry it in an OEM Blackberry holster for a BB9650 (Verizon). ~$8-9 from eBay. Works great.
IMHO, fashion is fine up to the point where it flies in the face of usability. At that point it suggests being overly concerned with what other people think of you.
Don't forget the free iPhone case program until 9-30-10 for iP4 units. I have a few cases I've tried, Silicone CaseMate one that looks like a tire tread, Naked Case in black, I have a brand new CaseMate Snap Case unopened. Right now I am using the black bumper I purchased when the iP4 case out (and Apple refunded me for). So far that's what I am rolling with.
I am on the pre-order list for www.elementscase.com Vapor 4 case Silver/Blue but the waiting list is 4-6 weeks. That is unless you go to eBay.
