It does not rely on special effects, though the ones it has are quite impressive. As mentioned in the reference it relies on good story-telling. You can also add a bunch of very vivid and weird characters each of whom is an "out-of-controller". The voice of Mab is extremely sweet and unforgettable. The transient effects are very creative. Like for example when a medieval soldier drops dead and the blood makes the snow change its colour around his body in a hyperbolic manner.
It feels like deep satisfaction to have it on DVD in one's home collection. Celtic legends, runes, the Lady of the Lake, Excalibur, and king Arthur – there is much talking about all that stuff now and then and here is a chance to see the whole story properly told.
There is also a strange feeling that it's not just a fairy-tale but a kind of history lesson as well. Even if it's a mistake to say so, this film is not historically empty.
Easily, it is an 8 out of 10. Thanks for attention.