I've never taken mine off.
OK, I just tried it. To safely remove the bottom half of the case, gently push the back corners to release the clips there,next spread the side clips just below the side cut outs just enough to release them. You can then gently pry the case away from the rear portion of the bottom, then slide the MacBook to the rear to remove the case bottom. You have to be careful to flex the case only enough to release the clips, any more and you risk cracking the plastic.
To remove the top portion of the case, open the computer and start with the top center clip, then the upper and lower side clips, making sure that the case top doesn't snap back in place. Once the clips are released, gently prying the case away from the lid, starting at the top and working down both sides should let you slip the case off towards the rear. I just tried this on my case and was able to safely remove and replace the case.
When replacing the case, follow the directions that came with it.
scifan57, iPhone Forums Moderator