I bought it the day I bought my MacBook Air. I have used it once to watch a DVD. It's not really "necessary", until you come across a time you really need to have a CD/DVD drive. It's more of a peace of mind thing for me, I know if i "need" it, especially when traveling it was worth the $91 I paid. I just wish it worked with other machines besides the MacBook Air. I have a Samsung Q1 UMPC that I plan to sell on ebay, and was going to blow it out, unfortunately the MacBook Air SuperDrive only works with the MacBook Air no other machines, including Macs.
If you really need a CD/DVD drive (mainly to watch DVD's ), it's worth it.