It's not terrible. It's just not particularly good either.
The aiming and movement compared to any good FPS on wii is god awful. It's sluggish as hell and feels like you're moving in a big vat of molasses. It was very uneven in it's quality of graphics and level design, the swordfighting was terrible, the story was cookie cutter action almost non-existent, the voice acting wasn't even B movie quality. The enemies were dumb as hell, the guns were uninteresting, there just wasn't really anything great about it.
Is it a bad game? No, it's perfectly playable, there is some fun to be derived from it, but that can be said of a hell of alot of games. It's not a travesty, but it's not going to be remembered as a highlight of the wii's line up and I would never recommend it to some one who just bought a wii and asks "What games should I buy".