I upgraded to Mountain Lion this evening. I cannot believe how easy it was. The longest portion was the download, which doesn't really matter since I could do other things while that was going on.
Once it was downloaded, I kicked the process off, then went and had dinner. By the time dinner was finished, so was my install. Incredible.
There are a million reviews out there already for Mountain including the legendary John Siracusa review. I will say that in the 30 minutes I've been playing around that I love that Reminders and Notification Center are now on my mac. Having Reminders on my mac makes it easier to quickly set up location based reminders to use later on my iPhone.
So in the span of 48 hours I've updated to Squarespace 6 and Mountain Lion and wrapped up 3 projects. Seems like I should be leaving on a high note.