The product is great in itself. It does it's job perfectly. Mouse response is unparalleled. Easy to clean, and doesn't wear anything like as quickly as other mats.
The only problems are that the glass it is made of is frosted and therefore quite rough meaning two things.
1) It makes quite a lot of noise when you slide a mouse over it.
2) It may damage the underneath of the mouse fairly quickly. Mice always get damaged over time but this mat may speed up the process.
Not huge problems really so all in all, a great product.