This product is really cheap when compared to others which are available. You may think that it might be a little dodgy as a result, but the truth is the hardware is solid, but there may be some confusion about the drivers which it requires.
It should come with a CD, but if it is faulty (mine was for the Mac drivers), here is a link to a website which can provide the Mac drivers only. (You will probably need the x86_64 drivers for modern macs, including the Air and Pro)
I tried the adaptor out, and it is zippy and I had no noticeable difference between the speed of this adaptor and my wifi connection at home.
Overall, excellent product, just might turn out to be a little tricky to install.