I was really looking forward to play Team Fortress 2 once it came out on October 10th and decided to read a lot of news regarding that release to be up to date. My heart began to beat like hell when I realized that it was possible to make the purchase at an discount right away and be eligible to play the Team Fortress 2 beta right away.
I got an 10% discount of the $49.95 retail price in October and was able to download Team Fortress 2 right away. This had another advantage: The rush on this game will be immense and it can very well be that the Steam servers will have bandwidth troubles in the first days of the release.
The other included games, Half-life Episode 2 and Portals have not been released as of now and have to be downloaded once the Orange Box comes out on October 10th.
I say that it is worth it. You pay less, get to play it early and can pwn all your friends once they get the game on October 10th.

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I love Team Fortress 2 that is in the Orange Box! My friend has already set up a server with co-location from Nationwide Bandwidth 67.90.47.47, (a must to every server owner, imo) and we are enjoying it with many other gamers.