Maybe it contains some prerequisite 2.0 stuff so the 2.0 update goes smoothly. Windows Phone (and a couple Android tabs) sent a mini-update before doing a version upgrade.
you never know. the last update gave the PB full tether over bridge pretty much and that was not included on any of the "release notes" so you never know what easter egg you might find this time.
This will be my first update. You don't lose the device info when upgrading do you? I have a TON of pics/videos/songs on the PB that I would rather not have to load again.