Typing accuracy - This keyboard does change the typing experience to some extent. Having gotten fairly comfortable with typing on it over the past few weeks, I don't mind the imperfections now. However, you are likely to notice that you miss a key as you are typing. Fortunately, most such mistakes are corrected with the auto-spell check, but sometimes it just picks up the wrong word, so you will need to be careful. The highest likelihood of mistakes occurs with keys on the top rows of the keyboard (qwerty keys). I guess this is because with your wrist resting on the Mac, the fingers fall on the top keys more horizontally (i.e. with less pressure) than they do on keys in the bottom half of the keyboard, where they fall more vertically (i.e. more pressure). I have average sized wrists and fingers, it's entirely possible the experience for someone with large or small fingers my be different.
Finish - After only 3 weeks of heavy use, some of the black color in the keys has already started coming off. Not a big deal so far, but I can see the letters wearing off within the next 5-6 weeks. Again, this factor would depend largely on usage time for each user.
The hole for the Caps Lock light is spot on, exactly where it should be. However, given the not-completely-transparent silicone material, the light is visible only if you're typing in the dark. At any other time, the light is so faded that it's not really visible through the cover. Same issue with the back light, the cover does dim the back lit keyboard somewhat. Either of these factors is not a deal-breaker for me personally.
All in all, given the price of this cover, I would be happy if I can get even 2-3 months of use from it. Most of the other such covers I looked at were priced at $20 plus, which I think is a rip-off given that it's only silicone. This product is a good investment in protecting an expensive device that I'm sure most of us would like to keep for at least a few years!
