I tried to resist but went ahead & picked one up. Already got confirmation that its packed & ready to ship.
I wasn't going to buy it since I'd rather try out the 24mm is. But after looking up the used prices for this lens, I figured (justified?) that I could play with it for a few months (or a year or so) & then sell it for a small profit.
If there turns out to be a problem with the lens, or the order gets cancelled or something, I'll come back & post. That way everyone that resisted can say thank god, or "Yeah, knew it was too good to be true". Or maybe, "HA! You get what you pay for!!"...
Mine arrived yesterday (it's nice that Philadelphia is close enough to Adorama's warehouse for even their free shipping to be next day) and, as I would expect from Adorama, appears to be a new standard US-issue lens. I've only had a chance so far to use it around the apartment at night, but it appears to perform flawlessly on my 6D and to be an excellent lens. A rare case of "seems too good to be true but true nevertheless." I trust everyone else who bought one had/will have a similar experience.
Anyway, I'm extremely grateful to the person who alerted us to this short-lived bargain.