According to 9to5mac.com OS X Mountain Lion it will be available. for purchase. tomorrow!  The cost for the upgrade – $20.

The word on the net is that Apple Stores might be a little behind and won’t be able to demo the operating system the same day it launches but for those who are ready to demo the new OS iPhones will be placed next to MacBook Airs so that customers will see how iCloud intregration works.

Along with the OS there are supposed to be updates to iPhoto, iMovie, and Safari.

Let the downloads begin!