I recently got a Desire S, which I am delighted with, and wanted to get some protections so that the aluminium unibody doesn't get scratched over time. I looked at several designs and eventually went with the Case Mate Barely There which arrived today.
The case is a snug fit and matches the Desire S perfectly, with cut-outs for the camera and flash, the speaker on the back, the volume rocker and the USB socket. The edge of the case is sculpted around the headphone socket and there's a notch where the mic is placed. The fit is so close that it's actually a fiddle to remove once it's fitted - you only need to do that to access the battery, SIM or SD card - otherwise everything's accessible.
Unlike many of the cases it's actually black in a satin finish and made of a flexible semi-rigid plastic - flexible but definitely tougher than gel. I'm not sure how much impact protection it would provide but the scratch protection is excellent and it actually improves your grip on the phone which can be a little slippery otherwise. The back of the case is embossed with a discreet but stylish Case-Mate logo.
It comes with a screen protector shaped specifically for the Desire S screen, though I thought this was redundant since the Desire S has a screen made from scratch-protected Gorilla Glass and using a screen protector might reduce the sensitivity of the touch screen. Still it's a nice addition and as it's separate you don't have to use it.
Overall I would say that this case enhances the Desire S and protects it too, which is exactly what you want from a case.
Full marks to Case Mate.