Paying for Content, Not for Time
I really like the Free to Play business model. I have no problem paying for game content in chunks. It gives me the freedom to spend the amount of money I want on the parts of the game that appeal to me and that's awesome.
In the past few months I've spent money on content for Tribes Ascend and Hero Academy. In Tribes I unlocked some classes and in Hero Academy I unlocked different teams to play with. In total I spent maybe $20 between the two games and it was money well spent. I unlocked some content and got to support good developers in the process.
I'm planning on spending a little more money on both Mech Warrior Online and Mech Warrior Tactics when they come out this summer. Depending on what's available in the Guild Wars 2 store I may spend some there too.
The coolest part of F2P games is that I don't have to spend money. These games are all designed so they can be played and enjoyed for free. But, once I play a game and have fun with it I want to support the developer while unlocking new content. I know in the long term this is how they'll stay in business.
The flip side is that I can no longer stand subscription games. The idea of paying for game time seems like a horrible deal to me. Renting time instead of permanently buying content... that just seems like a rip off. And that's what it really comes down to, paying for time or paying for content. I have no problem paying for content. But, unless something unbelievably amazing comes along I don't see myself ever paying a subscription for a game again.
For the foreseeable future I will most definitely continue to support the F2P model by buying game content in any game that I think is fun.