I received my iSkin keyboard protector in the mail several days ago, which was much earlier than I was expecting it to arrive. I've been using it for a few days now just to get a feel for it so I can give my review on the product. And, I have to say that it's pretty good! There isn't much for me to complain about.
The Pros: The iSkin covers the whole keyboard area, yet it doesn't add any bulkiness. The outside texture of the protector is anti-slip and doesn't add any new weirdness for when typing. I guess the flexibility of it really helps to move with the keys. When I was doing research on keyboard protectors, online reviews mentioned that it may take getting used to typing with the iSkin, but that wasn't the case for me. I instantly adjusted. The bottom/back is also made to grip onto the surface of your laptop so as not to slip. I can already see dust and little crumbs collecting on it instead of getting into my keys.
The Cons: There isn't much to dislike, except mainly its color. Although the rest of my new laptop is pristine and white, the iSkin has an off-white, yellowish tint that makes the keyboard look slightly dirty. I don't know if that's the case with everyone's or if the bottom of mine is just getting dirty already. Other than that, I don't know how effective the anti-bacterial function of the iSkin is since there really isn't a way for me to test that. And the price! It was a little expensive for the tiny package and its shipping cost. All in all, I spent just under $32. But if this prolongs the life of the keyboard, I wouldn't mind a little costliness.
Conclusion: This is definitely worth it! I give this a +4.5 on a scale* from -5.0 to +5.0.
Addendum: *I actually got this scale from one of the Fab 4. A zero is the neutral, middle point, while any positive number stands for something above neutral and any negative number stands for something below neutral. The max +5.0 means that something is incredibly amazing; similarly the minimum -5.0 means that something is disastrously terrible. We believe this is a superior scale than the ubiquitous 0-5 or 0-10 scales.