If your looking for a live action version of Yoshiki Takaya's long running Manga then your going to be disappointed. Howeverm if you've come looking for a great and original Sci-Fi film than your in for a treat. Sadly all but the image and mechanics from Takaya's original, but Guyver: Dark Hero is a wonderful story following Sean Barker, the Guyver - "infected" with the Guyver a alien armour that drives him to correct it's creator's mistakes, shape-shifting killer monsters called Zoanoids.
If you pick up this story and are a bit lost at first it might be worth mentioning that this is a sequal which, I'd recommend finding
The Guyver [DVD] [1991] [Region 1] [US Import] [NTSC] which sadly has only ever been release in the UK on VHS under the title of Mutronics back in the 90's.
All in all the film didn't have the biggest of budgets, but it doesn't disappoint for what it is. The creature effects are adequate enough not to look B-movie, but sadly are far from the terrifying creatures of Takaya's original. It's definately worth a watch, give it a go you won't be disappointed.