Well, if you're back on stock and really want to update, you can try the old fashioned method of setting your last recorded update back to 1969.

I think it's like this;

Settings -> Apps -> All
Google Services Framework => Force Stop + Clear Data
Back
Settings -> About Phone/Tablet -> System updates -> Check Now

No guarantee it'll actually find the OTA update so soon, since it just got released today. I don't even think it's officially on OTA channels for the Nexus 7 yet. Only Takju GalNex so far. You might need to repeat the above process a few times, though.

I'd still rather wait a few days first, just to be safe on application compatibility with 4.2

anyone knows where is Developer Options in 4.2? I cannot seems to find it.

Updated my n7 to 4.2.1, now cannot install from playstore, error from server...

from jb, the casing is included don't worry

I managed to persuade the EMobile salesperson at Yodobashi Akihabara Tokyo to release to me the official ASUS Nexus 7 dock made by ASUS! From Yodobashi online website, release date is pegged at 11 December 2012, but he quietly picked stock from storage and slipped it into my already bulging shopping bag so that he won't get reprimanded if anyone founds out he broke street release date.

Pic to come later. Need to catch the NEX bullet train to the airport.