Titan AE is one of the best non-Japanese animated movies I've seen in a long time. With a rousing soundtrack, some excellent choices as voice-actors, and well put together set-piece scenes, it's a highly enjoyable romp.
The plot is nothing particularly complicated, but then the film doesn't really claim to be anything other than a shallow but action packed extravaganza. The Drej are very well portrayed as an unsympathetic and seemingly invincible alien race, while you do get a proper sense of the impending doom of the human race after the destruction of earth (which is a great opening scene).
The film occasionally seems to find it difficult to decide whether it's aimed at adults or kids, leading to situations where you wish it hadn't pulled its punches at crucial moments, but generally doesn't slip into implausible sentimentality like many Hollywood movies do.
There are a couple of plot twists, but nothing too unpredictable, and while it's not a film you'll remember for a long time, it's certainly a fun way to spend a couple of hours. It doesn't even come close to the quality of any of the top anime movies from Japan, but certainly the best stab that Hollywood has had at a more adult animated feature. Well worth a view.