There's a meaningful distinction between 'pay to play' "can't wait" farmville, 'pay to play' random drop, tradeable, gameplay-available goods a la tf2, 'pay to play' cosmetics a la tf2 hats and hon skins, and 'pay to play' in-game advantages a la a lot of Korean MMOs and HoN's early-access hero stuff. Valve is toeing the line, HoN is straddling it, and Korean MMOs and "social" games have thumbed their nose at it.
But what Valve is doing is an improvement over the status quo, and social games are a regression from the status quo. TF2, by and large, didn't get worse by letting more people play it for less money - lots of value was created, and Valve is content to only capture a small* amount that came along for the ride.
*Many games that have gone F2P (in a generally benign way) report increasing revenues, e.g., Lord of the Rings Online, D&D Online, etc.
