Think it depends on the "free" model.

Nexus published games such as Dungeon Fighter Online and Vindictus have bad pay models. DFO, you can pay for additional credits to continue a stage, powerful healing items, and a random customization item (which is the most painful, since you pay real money for a chance to customize one character on one aspect of them and have to trade to other players in hopes to find your desired piece). Then Vindictus only allows customization that expires in 30 days. And both use a fatigue/token system for how many dungeons you can take on for the day.

DDO and LOTRO has a different F2P feel than Allods Online or Runes of Magic.