A total blast until you can't take anymore.
[Note: This review is of both Titan Quest and its expansion, Immortal Throne, together.]
Titan Quest distills everything that is addicting and innately fun about World of Warcraft and Diablo II into pure kill-loot-kill joy. It can get a little repetitive over time, but there's no question TQ delivers the goods so enjoy it until your brain can't take anymore.
First and foremost, TQ gets the classes right. Branching skill trees, varied play mechanics and dual-class combinations are a min/max-er's geek dream come true. TQ fansite boards are jammed with players debating which are the most powerful class combinations and skill tree selections, so the element of character building is extremely strong and fun and highly replayable. The game favors magic-users, but I was able to hold my ground fine with a melee/caster hybrid using the Defense and Dream Master masteries.
Secondly, TQ gets the loot right. Randomization of monsters and randomization of loot with rarity values directly taps into the sheer joy of opening chests and looting dead bad guys and wondering what splendors await to be picked up. TQ is awfully generous about it, too -- for players accustomed to gearing up at a snail's pace in World of Warcraft, you'll be pleasantly surprised by how fast and furious the gear comes. Optional trader NPCs in-game allow you to save great drops better suited for other characters by plopping said items into the trader's shareable slots.
And the last bright spot is how gorgeous this game looks. Environments are meticulously laid out with varying elevations, realistic details and impressive spell effects and monster detail. Titan Quest is a game all about making you feel good -- tons of loot, drop-dead gorgeous visuals, and simple mechanics that let you destroy waves upon waves of enemies with glee.
The downside, of course, is that Titan Quest gets incredibly repetitive mainly because:
1. The game mechanics are pretty simple. Each class seems to only have a few key attack moves.
2. Enemies may look different, but on a Normal playthrough, there's not a lot of variation in how you go about fighting them all. Some subtle tactical differences come up -- and supposedly gets more pronounced on the harder Epic playthrough levels
Both of which combine to feel like you're just endlessly slogging through things after a while. And obviously because the game is a single-player action-RPG, you lose some of the personality and diversions that online-based games like WoW and Diablo II otherwise keep you mixed up with.
All in all, Titan Quest is an excellent game to enjoy for a limited time. I'm sure hardcore Diablo II fans will get a bit more out of it than I did, as well as players who love the core gameplay and don't get easily tired of it over time. There's really no memorable story to speak of, so your only motivation here is loot and kiling things over and over. For me, that's fun for a few nights ... but eventually it's time to move on.