Nope, no case for me. I've had it for 3 weeks now, and it's still in perfect condition. Fits perfectly in my pocket. It looks better naked IMHO.
I will be purchasing a belt holster case so that I can use it at the gym, but not until I find the right case. The cases that the Apple Store sells just doesn't cut it for me. I'm using my nano at the gym for now.
I have never cased any product of mine. Whatever i buy, its always very pretty, and why would i wanna cover that up? I'm very careful with my electronics, and mistakes happen, but we all live through it.
Invisible Shield. Scratch and scuff protection and the phone still looks naked. I haven't dropped it once since I got it on the 3rd of Feb which is really surprising for me. I've always fallen victim to the "get out of the car with phone in your lap" drop.
I have an Agent 18 case which I "added to" (okay, I'm a girl, I like pretty things...). I have a horizontal Treo case with a belt clip that I use to carry it around.