This isn't the official OTA, but it is a official release. If it wasn't one would not be able to install it without rooting. I know it isn't the official release because I cannot access my touchdown key. I remember going through this when I had my nexus one, went through a few final releases, but when the release one finally came out, it was a small number, and I was able to access secure downloads from the market.
I think one of the things they will be fixing will be the final upgrade part, I've put this on 2 phones so far, and the 2 things I've seen is the launcher has a fit when upgrading from froyo (so much so I had to wipe one of the phones), and the sync icon keeps going unless one wipes it (I read somewhere that this is due to the email formats being different).
Now as far has the build it's self. It is more stable than froyo was for me, and MUCH faster. Since it is a official build, I will think that we will be seeing both the upgrade and full version of the downloads in the next few weeks. That's how it was for the nexus anyways.
