I preordered the Orange Box and I have to say, TF2 itself is worth the 45 bucks. I haven't been addicted to a game this much since I played FS2. Then we got Peggle Extreme which is pretty awesome in itself. Very entertaining for just two games; it's definitely worth preordering and saving 5 bucks. I'm already extremely satisfied but Portals and EP2 are still sitting there waiting for the release date on Steam. The Orange Box is the best thing since sliced bread and of course, FSO.
TF2 is just pure fun. They designed the game to be fun and less about competition. Even the models look silly and hilarious. This game is just built for pure fun. All the classes are fun to play and at least one of them will suit your gaming style.
Not to mention, you also get HL2 and EP1 as well. And if you already own them, you can even give them to a friend of yours. Preorder it now and get Peggle Extreme while saving 5 bucks.