One of the questions that was unknown until this AMA was how much free storage would be available to consumers after Windows RT is installed along with Office and the default apps? Ricardo Lopez, Test Manager for Surface RT has indicated that after all of that software (which comes pre-loaded) is installed, consumers will have more than 20 GBs of free storage available. Additionally, with the SD card slot, you can add additional capacity but it can only be used for music, photos, movies; you cannot install Windows 8 apps directly to the SD card.
So, if you were worried that Windows RT would consume too much storage space and that 32GBs would not be enough for your needs, ~20GBs of storage should suffice for most users.
If you have any questions that you would like to ask the Surface team, make sure to head over to Reddit (link below) as they team will likely respond to you if you ask an insightful question.