Case, skin, messenger bag. I use my rMBP for my business and school. I also ride a motorcycle when the weather isn't crap so it's constantly in and out of the bag that has other things in it and it's not a computer that just sits at home. In fact, it's at work with me sitting on my desk right now. From here it will go to class, then home where I'll edit some photos for a shoot I did, back out for another class, then home for more editing or homework. I'm not going to risk it getting scratched to hell and depleting the value because of it getting messed up.