I have the greasiest freaking fingers on the planet, and my black 5th Generation iPod is perpetually filthy, unless I wipe it incessantly on my pants. My new iPhone? Always looks pristine.
1. Choose white. Trust me, it looks better in real-life than it does on the Apple Website. With the chrome side & Apple logo, it looks like retro porcelain. White barely shows smudges, especially compared to black. I’d imagine it won’t show scratches nearly as badly as black, either (or the aluminum-look of the 1st-generation iPhone).
2. Buy and put on the matte screen protector (Power Support Anti-Glare Film). True, the iPhone screen is very durable and rarely scratches. But it does smudge very easily. The matte screen hides all but the most egregious smudges.
The Scobleizer agrees (at least on #1). He learned the hard way.