Absolutely amazing game. Recently completed this with a freind in co op mode and we really enjoyed it. The graphics are amazing for Wii, the music and effects too - overall production throughout is top notch. A big thing usually is controls, and they work effortlessly. In response to the review about bugs, well we didn't come across any at all, and it didn't crash once. Though I have had some games that have done that. Also, it is an on rail shooter, so it is a little unfair to mark it down if you just don't get the on rail thing.
But all in all, this is a game that will stay on the shelf for us. It was engaging, fun and a blast to play. The game starts off more with a story and paces it self so, and gradually ramps up the action along with story twists and new weapons - which have alternate firing mechanisms. The only thing I would recommend is setting the difficulty to Hard. The only thing I could gripe really is the difficulty at times even on Hard. This is probably down to how much of a gamer you are, but it may be a little easy at times to accomplished ones. But saying that, it does have some parts that are generally tough and ones that you have to go through a few times.
In relation to replay value. Having completed the game, you can play ten stages in which you just blast through hordes of enemies. This was better than we expected, and there is a high score to beat. Each lasts ten to fifteen minutes. We are also going through the game again on Impossible mode, and it actually gets better this time round, as it tests you more and getting through is more of a close call each time.
I hope this sells well, as we love this game, and hope there are more mature titles to come on the Wii.