I bough an iCarbon skin for my wife's 11" Air. It looks awesome and it'll provide good protection- it's fairly thick for a skin, and the carbon fiber (or faux cf, doesn't really matter to me) is textured, so I don't think any scratches are getting through.
One problem I noticed, though, is that the cut-out isn't exact. I thought I was doing it wrong, but when I applied the skin to the bottom, it's obvious that it's off by one or two millimeters (the cut-outs for the feet don't line up). So, covering the lid, it extends about one millimeter longer on one side than the other, and on the bottom, it looks good except some space around two or three of the feet. And the white Apple just isn't the right size- there was too much space left over, whereas I thought it would fit snugly, so I didn't apply that.
I would buy it again for my MBP that I'm using, unless I can find something very similar that lines up perfectly.