The MacBook Air 11inch is by far in my opinion the best, most portable Notebook you can buy. However, because it's so thin it takes out everything that is "extra space". A bit like a small car, if you like, it doesn't have a big boot to cart around, so too does MacBook Air, it doesn't have an optical drive as you don't need/use it all the time.
The SuperDrive is an excellent compliment to your MacBook Air for when you do require to use an optical disk. It is an excellent design and will fit in any laptop/notebook bag along with your MacBook Air.
I purchased a second-hand Apple SuperDrive from Amazon and I am very pleased with the product, it does what it says on the tin and is the best optical drive to get for your Macbook.