See i'll act against that because F2P annoyed me when TF2 got it because it added alot of noobs and made me feel upset that i'd paid but they haven't.
The way I look at a purchase is amount of time spent vs money spent on it.
I aim for a £1/hour of play ratio, seems fair enough. I paid £15 for The Orange Box on Christmas 2007. As of this post, Steam Community Stats tells me I've spent 1184.4 hours playing Orange Box games.
This works out at just over £0.01 per hour. This does not include time spent in the Source SDK, nor does it take into account money I've made from The Orange Box (Swamp Theme).
EDIT 2: Just done the math, with these, I've been making just over £0.07 an hour! Woo!
Overall, I'm pleased with my purchase, and I'm not annoyed at all for it going free to play. If it means there is more time to enjoy the game I bought (nearly 4 years ago!) with a kickass community, then I'd say my money was well spent.
Probably the best £15 I've ever spent.
EDIT: But yeah, on topic; CS! Woo!