A F2P MMO profits by making items available that will put wealthier players ahead of others. Some MMOs implement a more even playing ground than others, which is nice, but most don't.
The best way to do F2P is to basically make it "subscription-optional." If you spend the price of a normal subscription each month, you should get the expected benefits of your run-of-the-mill subscription MMO.
But having played so many F2P MMOs, I despise the model. It's terrible for any game involving a huge investment of your time. The developers care far less about patching the game and rebalancing because their incentive, their guaranteed revenue, is gone. On the flipside, they have more incentive create a ton of expansions for that guaranteed revenue, usually expansions they put together as quickly as possible so they can move on to the next.