I like Turbine's model for DDO and LotRO; Early content is free. As you play said early content, you earn Turbine Points (currency which can be used to purchase later content). As such, if you're determined enough, you can unlock all content without spending one cent of real world cash. Though IMHO, if you're drawing this much "enjoyment" from the game that you'd grind for TP, you should throw a little cash their way in appreciation for their work.
However, since later content is bought a la carte, it can be difficult to find people to form a group with the exact same content as you. Especially in LotRO, where the majority of the quests are one-and-done, whereas in DDO, most non-raid quests can be completed over and over until the cows come home (with diminishing returns, of course).
Edit: The one big downside to F2P games, now that I think about it, is that it allows anyone to play the early content. While this means there will be new people who want to play and get better at the game, it also means more noobs. Which generally causes me to turn off the general/ooc/trade/etc. filters off when crossing newbie/lowbie content areas.
However, since later content is bought a la carte, it can be difficult to find people to form a group with the exact same content as you. Especially in LotRO, where the majority of the quests are one-and-done, whereas in DDO, most non-raid quests can be completed over and over until the cows come home (with diminishing returns, of course).
Edit: The one big downside to F2P games, now that I think about it, is that it allows anyone to play the early content. While this means there will be new people who want to play and get better at the game, it also means more noobs. Which generally causes me to turn off the general/ooc/trade/etc. filters off when crossing newbie/lowbie content areas.