It didn't start out well. Okay-ish, in a "that was quite crap but could go somewhere" kind of way, but unfortunately the "somewhere" in question was "down the toilet".
Mainly, the problem is that the characters don't do anything remotely intelligent. They're doing cliched things instead, more because it seems expected of a TV programme at that point, than because the characters or even the story has driven it to that point. katlinel said, "this is written for children, isn't it?" And everyone knows they can't tell when they're fed any old rubbish...
The tragedy is that the character animation on the creatures is pretty damn good, so they've wasted so much effort in the effects, and ignored the writing. Bah.
In interviews, the makers are at pains to point out that this isn't Doctor Who. They're damn right about that. Alas.