simple blasting action, loads of fun

Yes

amazing story and gameplay 8/10

Overall I liked it and got my money's worth. I got it cheaply a while back, so recommend not spending too much on it. I'm not a power gamer and still finished it quickly on Normal mode. I'd assume that the hardest mode would take longer due to fewer health packs, ammo drops, etc. along with harder encounters.

Pros
-- Fun using the TMD powers, especially the timestopping bubble thing.
-- Fun puzzle elements where you have to age/de-age things and move stuff around to continue
-- Cool weapons, although I had some trouble using a few very well.
-- Interesting story with little tidbits found on recording boxes throughout. Reminds me of a mashup of Fallout's retro vibe with a mutated/demonic/evil creature FPS.
-- Lots of hidden locations with goodies

Cons
-- Boss fights. I personally hate this in any game, so your view may be different if you like that. I generally got through on my own, but had to cheat a couple of times to get past a couple.
-- Very linear story line until the end, but didn't mind this too much since I like narrative aspects of these games.
-- Very little ability to modify terrain or move outside of prescribed areas for tactical reasons