<A target="_blank" href="http://www.wired.com/gadgetlab/2011/07/os-x-10-7-lion-ditches-the-disk-offers-cloud-only-recovery/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+Index+3+%28Top+Stories+2%29%29">OS X: 10.7 Lion is now available.</A> The 3.5GB upgrade is not available as a disk. This may cause some difficulty if your machine dies mid-way, as there is no recovery disk.