I'm pretty excited about the update. The pink coins especially are cool. I wonder how many you can have in a level, and if they carry over from between sub-areas. I'm guessing "five" and "yes", respectively. Also it's interesting that keys don't have to be carried, but just float along with you. I guess that had to be the case to make them work with the original Super Mario Bros.
I will once again lament the absence of some really obvious stuff the game should have. Today's complaint: you should be able to place blue coins, a.k.a. coins that only appear once you hit a P-Switch.
EDIT: A new video was uploaded; 5 pink coins is indeed the maximum per stage. Also you can hold up to 8 keys at once for some reason. Looks like pairs of doors remain permanently unlocked, though, so I'm not sure why you'd ever need more than fou—oh, right, it's 4 sets of doors per area, so you might need 8 keys after all. Guess that means you can take keys through pipes.
EDIT: Correction: it appears you can have 10 pink coins total, 5 in each area. But they all stack together; you need all of them to make a single key.