I signed up on USCIS website to get updates via email.
Last email said my card had been produced on 18 June and picked up by USPS for Priority 2 day delivery.
Supposed to arrive tomorrow, 20 June 2014.
The card was produced and picked up by USPS in Corbin, Kentucky.
I didn't ask for, nor pay extra for Priority delivery, so I guess that is the standard way they send the cards.