I have been attempting to install Xcode 4.1 from the app store on my iMac, recently upgaded to Lion. On the first two attempts, after 12 hours of waiting to confirm, the install locked the machine and the only way out was to power off. On powering back on the hard disk was trashed but I was able to restore from my Time Machine backup. On the third time I ran the .mpkg installed from within the .app package and again after 12 hours a power off was required. This time I discovered that all my Time Machine backups had been deleted, my SuperDuper clone on a firewire attached drive had been deleted and all the files on two NFS network drives (on a QNAP SAN) had also been deleted. So... despite being 'belt and braces' on backups I am now left with nothing. If anyone has any experience of recovering from this kind of disaster using Disk Warrior or similar I would be grateful for any advice that you can give. In the meantime I am waiting for an onite visit under Applecare so maybe they can do some recovery. But my advice is do not try this install, there are other discussions about how this install can crash and trash the disk but I haven't seen one where it's trashed all attached drives. Apple have known about this for months, I cannot believe that this code is now freely downloadable with this kind of bug contained within it.