Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
From what I've read, It doesn't scratch your mac as long as you take it off every week or so and clean the case and your mac.

I plan to buy my macbook pro this month and will be picking up a speck case for it. Protecting the 1300 investment.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.