Lots of my university friends used this type of leather/plastic covers for their 13 inch Macs. I didn't like it at all and my friends also gave up on cases in 2-4 months.
The reason it is bad for you:
1) Heat dissipation is lower in a case: bare laptop metal reacts with the air and cools down faster. Laptop in a case felt warmer most of the time, because plastic/leather is worse at heat dissipation.
2) That cover on the display will eventually kill the hinge. Apple designs the products and certifies the accessories. Apple do sell Iphone cases but it is reluctant to offer one for Mac - added extra weight to the hinge will definitely not add a life to it.
3) Weight and bulk. All of the 13 inch owners(my friends) gave up on the cases because of this single reasons. Their 13 inch light macs almost became like 15 inchers - its' footprint is bigger and the weight is noticeably bigger as well.
I would rather buy a leather sleeve if I had money to burn. Because the most scratches might come from transportation and it is a less chance to ding your laptop while it is seated on a desk. But going in and out of a backpack might scratch with a zipper.
