it's worth playing again, imo. did you even get to the part with the marines after you and stuff?
definitely some really cool stuff. but if you really hate the "jump this, climb that", then you probably won't like it much, i guess
i got to the part where there was a 3 leg alien coming out of the ground trying to claw the heck out of me and you had to distract him, i turned on that generator, then i did a couple of bad game saves after being too lazy and at that point i didn't really care
ah, i remember that dude. he could hear you, so you had to walk so you didn't make noise. and you could stun him with some grenades.
i feel your pain on screwing up saved games tho.