At the moment I am set on bying an MBA 13. Since I plan on using it as my only computer and plan to have it for several years I should probably go with an Ultimate 13. The thought that struck me though, is if the 128 GB SSD might actually be enough. I examined the data I have and it sums up to roughly 38 GB of documents, iTunes and photos. Correct me if I am wrong here. I read somewhere that the basic OS X installation and iLife is about 12 GB Setting aside another 10 GB of space for applications like iTunes, Open Office, Pages and other utilities would bring the grand total to 60 GB. With a formatted drive space of about 120 GB, I would have around 60 GB free space. How much is a good idea to have as free space on your MBA to keep it snappy? I have read both 20% free space and 10 GB free space as advice.