Just created an account to say that I have an Air, Pro, and iMac that were all updated and sent through infinite cycle updating loops. I reinstalled OS X on the Pro last night and it is running smoothly. I tried reinstalling OS X on my Air and iMac this morning but the reinstall failed multiple times on each device. Each time I would run reinstall the estimated times would fluctuate between 1000's of hours till completion to 0 seconds before completion. I allowed each reinstall program to run for several hours and no luck.
I was a big Apple fan boy and I've converted so many people over the years. But now, I give up. So many issues, so many problems over the last couple years. I throw in the towel. I wish you all the best Apple.