Thank you
Max capacity depends on SD memory card you use. These memory cards are the same used on digital cameras: you can find a 128 MBytes one for low price. In order to run gba demos, sadly, you must have a gba flash card, because different memory location used to load roms
AFAIK, the good thing is that no passme is required and nor firmware update is needed to run ds roms.
My MK2 will be shipped "when september ends (TM)", so I can't say much...