If you have the game, great. Go get Titan. If you don't have the game, you might want to get into the free weekend for Unreal Tournament 3 Black, which is the game, the 2.0 patch, and the Titan Pack. All you need is a Steam account, and you'll be able to access and play it for free this weekend.
Should you love the Titan Pack -- and I think you will -- and want to purchase it, you'll be pleased to know that Steam is also running a sale through March 15th, where Unreal Tournament 3 Black will be 40% off. That's $11.99 for a whole bunch of game.