[lukefreiler]

I don't think the argument above has to do with the model of "unlocking things". The difference in League of Legends (and DotA2/TF2) versus most other contemporary (especially mobile) F2P models is that most of what you buy (your example being Champions) are permanent unlocks. I haven't heard a lot of arguments against that model. You're paying for a digital version of something that you now own, you keep, you collect, and you can essentially use forever. To me that's very different than buying something consumable (e.g. coins) or energy based that is literally spent and then gone, at which point you're expected to pay more.

More importantly I agree that this model heavily encourages the developer to design around that methodology (well described as "gamed" above).

To be fair, in this specific example - if I recall in Triple Town, the main thing you bought was unlimited play-time ("turns") for $3.99 (which follows the more positive unlock model). After that you could buy the standard coins (the shitty model), but given the design of the game I never understood why you would.

[StavrosK]

Not only that, but, in DotA 2, it doesn't actually affect the game. It just looks cool.

[dkersten]

Even buying champions in LoL (you can buy skins too) doesn't affect the game really because every week the champions you get to play for free rotate, giving everyone a chance to play whichever they like and secondly, they are balanced so that it doesn't really matter which champions you play if you're skilled. You are really paying for a different experience.

So, the three models of free to play that I see are:

1. pay for perks - this is the traditional "you pay and you get something you can use", be it guns or coins or whatever. The danger with this model is that it is a very fine balance to prevent this from becoming pay to win.

2. pay for cosmetics - DotA 2 or skins in LoL or hats in TF2 or whatever you have. Buy things to change the look of your stuff in game, but buying things has no effect on your success or the gameplay. IMHO almost all free to play games should support this in some way.

3. pay for experience. The things you buy in game don't give you an advantage in the game but instead alter the play style or how you experience the gameplay. League of Legends gives you weekly tasters of the different gameplay experiences the different champions have to offer and you can pay to keep the ones you like best. I believe that this is the model (coupled with #2) that ultimately makes the very successful free to play games stand out from the merely moderately successful ones.