Bought this for 20 bucks. I bought it solely for Half-Life 2 and Episode 1/2. With the amount of time I've already put into it, the 20 dollars is justified. Portal is a great game too, so that's nice. It was also a pleasant surprise to see some people are still playing TF2. I own TF2 for PC so I won't play it much, but, for some extra achievement points, it'll be nice.
And I will be buying these two off the Steam Early Holidays for less than 10 bucks. I LOVE Steam.
Best part: I almost bought Mirror's Edge for 360 for 20 bucks, but decided I'd wait until Steam Deals were done. Thank gosh I waited.