This is the first official and confirmed update of this algorithm but I do not believe this is the first time they actually ran an update on this algorithm. I believe they ran updates and refreshes to the page layout algorithm before but haven't told us. Google has been in a telling mood and told us about this data refresh.
Why do I think this wasn't the first update? Well, when I ran a poll in June about recoveries for this update, 21% said they did recover - and the only way for them to recover is for Google to push out a refresh OR if they webmaster confused this update with another.
Here is Matt's tweet:
Minor weather report: Update of goo.gl/OpIDL launching today. ~0.7% of English queries noticeably affected.— Matt Cutts (@mattcutts) October 9, 2012
Now, the biggest complaint I am seeing is that the updates are happening so fast and on top of each other. Honestly, I think this is typically the case, but recently Google has been very interested in announcing these updates.
Let's take a look:
As you can see, there is a lot going on recently with updates at Google.
I personally would not label this page layout update a second update, I wouldn't be surprised if this was number 3 or 4 or so for the year.