A new interview with the chief of operations at Flagship, Max Schaefer, is up at Eurogamer MMO and it has some nice tidbits on how they hope to implement micropayments in the free-to-play Mythos, as well as a piece of their development roadmap.
Max mentions that instead of just selling items, their focus will be on selling enhanced functionality and things players can opt for to get a greater chance at advancing more quickly or have a better chance at finding better loot. Examples given include stash enhancement -- the stash being the storage treasure chest each character has available to them -- such as larger stashes and stashes shared between accounts (so you can have your melee-focused character hand over that great magic staff that is otherwise useless to your magic-wielding character via your stash). Another example would be buying the map to a particular area or dungeon that has a high Luck associated with it, meaning the chance of valuable drops is higher. (Maps operate as keys to new areas -- sometimes marked as "temporary" on the map if they're instanced -- so if you don't have the map you can't go there.)