Simply put, the Orange Box is an excellent set of games, but this version happens to be the weakest.
Allow me start with the media darling right now, Portal. Portal is a very good game, but in my opinion it's the lowest value of all 5 games. Don't get me wrong, it's extremely entertaing and it has an excellent game mechanic, but it is a brief adventure. Really breif. I'm talking about 5 hours at most and about 2 to 3 hours for those who are good at solving puzzles. This game's humor is mostly hit or miss, but you would have to be insane not to enjoy the end-game song. A very good game, but it's not even the second best game on the Orange Box.
Team Fortress 2 makes no attempts to tell a story, but rather throws you in the middle of the 2nd best shooter to come out this year. Balancing is excellent, the graphics are crisp and thanks to a recent patch, online play is smooth as silk. Just plain fun, even if I wouldn't have minded slightly more interesting maps, but now I'm just nitpicking.
Half-Life 2, for those of you who haven't played it, is an experience not to be missed. The levels are linear, but perfectly designed and complemented with excellent set peices. I can't stress enough how well designed the levels of this game are, it really will amaze you. The story is strong and the action is stronger. It might seem boring from afar, but it is truly an exhilirating game. Just make it to Ravenholm, then you'll understand exactly what I'm talking about.
This games got it's fair share of bugs, however, especially the loading times in half-life and portal. Don't let that scare you, any performance issues are totally worth it, this game is simply the best value on the PS3, rivaled only by The Elder Scrolls: Oblivion. Do yourself a favor, buy this game and you won't feel a need to play anything else for months.