i seriously researched for days just before i purchased my MBP 13" - i was debating between the seethru satin and the clear hard case. After trying both at the store i think the satin has a better feel/look than the clear. mind you that the satin is actually a clear/hard case with a frosted outside, it seems. so the protection is there. alot of people mention that it adds alot of weight, i think it feels fine.
the reason i didnt want the clear hard shell cases was cuz it looks a little to tacky for me, that shine on it kind makes it look weird, for me at least.
another case i was looking into was the incipio feather, but the bottom shell has no holes for the computer to breathe, while that may not be an issue in reality, the heat that i get from my laptop already probably wouldnt have been good with this type of case. another reason i didnt get it, was cuz the case is a lot thinner than the speck. i could easily see it bending and warping over time. as far as the looks, it looks a lot cooler cuz its a solid color compared to teh satin. however i dont mind the red speck that i have.
goodluck, i know people that are fine without cases, but for my own piece of mind, speck keeps me safe, and it looks cool too!