from a technical point of view they're a professional, tight band. thematically, they feel a bit gimmicky, even though I'm sure their hearts are well into the music. still, at times they feel too much of a "themed amusement" act like Finntroll or Korpiklaani.
that said, going back to the overall picture, they have obviously grown as musicians, each album grows more complex and technical, exploring new musical colours and shades each time, experimenting with new ideas. it's a collective that doesn't rest on any laurels they've achieved, not to mention the subject matter is quite a fascinating area.