1) At least in the US, I don't think it's out yet. I have a rental 16-35 F/4L IS on order from LensRentals (at first availability) and they keep pushing it out as stock has not yet arrived.
My planned rental comparison (as I lack any ultrawide right now) is to stack it up at 24mm and 35mm against my pretty damn sharp 24/70 F/4L IS at F/4, F/5.6, F/8, etc. If the MTF charts are any indication, the new 16-35 should beat the 24-70 quite well in the corners at same apertures.
I also plan to see how wide I can shoot that 16-35 and not see vignetting with my Lee setup. I'll run combinations of 2 slots + CPL ring + no polarizer, 2 slots + CPL ring + CPL in place, etc and see when I lose the corners due to obstruction.
If (a) it's as sharp as billed and (b) obstruction with the Lee setup only occurs wider than (say) 20mm, I will buy one straightaway.
2) Some gentleman in Malaysia got his hands on a copy and made a video about it, see this other thread I posted: http://www.canonrumors.com/forum/index.php?topic=21284.0
I also have a daily Google troll of 'canon 16 35 ("hands-on" or review)' with a date limiter of the past week. Little to no activity other than forum discussions just like these.