There are a lot of different manufacturers out there offering skins and it is hard to tell a difference. Gelaskin has a clear description of their skins and quality:
GelaSkins are a very thin (< 2mm) protective cover for your iPhone, iPod, laptop and RAZR made with premium grade 3M vinyl and adhesive technology. Patented micro-channels within the adhesive allow for a bubble-free application. Each GelaSkin has an ultra-clear, scratch resistant coating for maximum durability and photo quality finish.As you can read out of this quote Gelaskin offers these skins for iPhones, iPods, notebooks and RAZR cell phones. On top of that they produce screenguards for the music players and the iPhone.
All of their designs are created by a group of artists, so the designs offered are exclusive to Gelaskin. The list of designs offered is actually quite extensive.
The Gelaskin ships in a clear plastic bag. To keep it from folding or bending during shipping, it has a solid foam spacer behind the sheet holding the skin. The rear has some illustrations of other designs available. While the package is very simple, it is certainly quite effective.
The other sides of each sheet have some additional information. The one holding the sheet has the 3M logo on it, while the other points you to a website where wallpapers, which match your Gelaskin, are available.