M13 cards have now been added! http://www.mtgprice.com/spoiler_lists/M13
You should be able to add them to your collections immediately.
More generally, our goal from this point onwards is to have new sets up and running by the Thursday before the pre-release so that you can trade during the day with certainty about how much a card is worth. We are also going through odd sets like the “versus” releases and the individual DCI, FNM and arena cards and adding them in – aiming for around 1 week from now for those.
Also we have fixed a few major issues – you should see most vendors have prices on most cards once again. Also, if you have signed up for the early beta to track your collection, adding a new card should have more detailed card incformation (rarity, color and casting cost as well as type) – this information will be added to the set lists within the next day or two.
As always, please keep filing bugs and voting on issues – we greatly value your feedback!
EDIT: Please note that prices won’t return to normal (with all vendors) until tomorrow.