Fun and challanging but it has clear problems.
But it is true that the final battle was dissapointing and seemed very rushed and the game felt short, and the story was quite weak but the gameplay was great.
A game where you have the power to manipulate time might make it sound easy for a fps but it worked really well. You can't just walk into a battlefeild stop time and take every one out because the npc's are in tactical positions and your powers wouldn't last long enough to work out where they all are. You can take different approaches to battles, which may not allways seem to obvious.
The puzzle aspects arn't say as good as they are in half life but theres no repition and it's keept challanging.
It's not too easy to review because it's not good in the typical way everyone would expect a good game to be, just stay open minded and you should enjoy your time playing it.