Great concept, terrible execution
So that's the good - unfortunately there's lots of bad. The graphics are basically early PS2 quality. The AI is abysmal, it almost seems as if it's only partially programmed. The story, characters and cutscenes are all a joke. Thought the platforming mechanics work well, the shooting is very clumsy. It's one of those games where you can be aimed 1" to the left of a guys head, then just breath on the controller, and now you're aimed 1" to the right of his head. If someone comes running at you and you try to aim and shoot while running backwards, well...good luck with that.
So it's positively crappy in most technical areas. However, for me at least, the core gameplay concept was so good that I still enjoyed it a fair amount. I think the level design was excellent, and picking off a few enemies with the sniper rifle, then figuring out how to climb / jump / advance through an area, killing a few more enemies as you're doing that, then being presented with a new environmental puzzle - I had fun. There are a pretty good variety of environments, unfortunately they're all rendered in fairly dull shades of color so they look fairly drab.
Overall, although I wouldn't exactly recommend it, if you're willing to overlook a huge load of problems, the core gameplay is worth it.