Strange that I have to rate how fun this 'game' is! Can't you tell this isn't a game, Amazon? Oh well, never mind. On with the review...
Functionality:
This protector fits snugly and unobtrusively around the 3DS, and is tough and sturdy. It is also very resilient to little scrapes as they seem to just rub away! It does collect little bits of dust, but that can just be swept off. It doesn't block any of the 3DS functions such as cameras, ports and lights. The triggers get covered, which was a bit difficult for me to adjust to at first. That might be the only possible downside to this product. You won't be able to use the 3DS charge station with the bottom half of the protector still on so take off the bottom half (leaving the top half still attached to the 3DS) and flip it up over the top. When you're done charging you can just flip the bottom half back over to the bottom of the 3DS and off you go.
Ergonomics:
It is very comfortable, and doesn't feel like it's about to slip out of my hands and smash on the floor! It did take a little getting used to at first, but don't they all? I don't find them at all troublesome, however, and the added protection has already come in handy with one or two clumsy people I know (name no names XD).
Appearance:
I don't think it detracts from the look of the 3DS at all - in fact I'd go so far as to say the protector looks good on it. Definately get black, as it will go well with any 3DS colour - especially metallic red!
Verdict:
Overall this is a great buy. Keeps th 3DS safe, feels nice works well. It also means that if, one day in the far future, you decide to pass it on or sell it, the outer shell won't look like an ice skating rink! I would definately recommend it.