It supposedly fixes a lot.
Here is a list of all the fixes http://support.vzw.com/pdf/system_update/droid_2.pdf
Here is a list of all the fixes http://support.vzw.com/pdf/system_update/droid_2.pdf
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
I didn't receive it. I got tired of waiting and just flashed the 2.3.20 SBF. Battery life was already good for me and this update made it even better. I also like how they raised the lock-screen slider like on the Droid1.
How'd you flash it?
The SBF File has been uploaded:
http://androidforums.com/droid-2-all-things-root/208711-droid-2-sbf-2-3-20-a.html#post1820304
Then you can follow these instructions as far as SBFing:
Tutorial/Walkthrough for flashing an .sbf to Droid 2 (unrooting/factory restore) - xda-developers
You don't have to root to run SBF. I was rooted but SBFed back to Stock 2.2. Never rooted my phone and then flashed SBF 2.3.2. It's running fine and I'm probably going to root it tomorrow.

My phone wont update. Will verizon update it for me if I go in?
As of this afternoon, mine is updated and re-rooted.
Anything of note?
Depends. I've heard that this pre-release was a test group more than a full blown OTA update. In which case the answer would be more than likely no. If in fact it is a full blown OTA, then you could push the issue at your local store. Afterall, there is a reason why they do it in waves.
Proximity sensor? What's that? This update supposedly fixes that.
Verizon has information on it on their website. Even steps on how to update over the air.
http://support.vzw.com/pdf/system_update/droid_2.pdf
http://support.vzw.com/pdf/system_update/droid_2_instructions.pdf
So it is an official update.
The initial wave of updates was a test to ensure it wouldn't be a buggy OTA. Now that they've gone nationwide, it's a lot easier for folks to simply go to their settings and pull the update.
That's what make the screen turn off when you're holding the phone to your face. It reduces the chances of you hitting a button with your face when on a call.