I somewhat agree with the OP. The combat was pretty awful. Putting points into stuns and the plasma ammo/damage kind of helps. It was quite infuriating when you'd be fighting 4 waves of enemies, and the last guy pins you against the wall forcing you to do the whole section over.
The movement and platforming also stuck out for me. Monkey doesn't move very well, it's hard to describe in words, but play any good 3rd person action game and compare it to this. It'll be like night and day. There seemed to also be arbitrary places where the game decided you can't run here. Speaking of arbitrary, we get to platforming. It's pretty obvious they were trying to be similar to Uncharted here, but they went wrong in several ways. First, and most egregious is you could only climb on designated pieces of terrain, and it was pretty black and white. Why do you need to be in a specific spot to climb down from a ledge. Why does he just roll half the time when I try to climb up to a ledge. Why can I climb up this pipe and not that one. etc etc etc. Now Uncharted isn't perfect in this, but it does give you some freedom to use platforming beyond the linear set platforming path. Also it just felt pointless, you point the analog stick in a general direction and mash X. Monkey is never going to fall off a cliff, or jump too early, or jump if there is no platform.
The game was also pretty buggy. The sound especially. Often the voices were out of synch or absent all together. The sound effects had similar issues in both gameplay and cutscenes. There was also a weird bug where sometimes you wouldn't be able to move right after a cutscene. Got to experience all of these a bunch of times while redoing that first Cloud chase sequence a bunch of times. The bad framerate was also pretty nauseating. Especially when you constantly have to swing the camera around looking for orbs.
I'm surprised you were told the ending was good. I thought it was awful, and didn't really make much sense in the context of the rest of the game.
I still ended up getting the Platinum, so I guess I liked it to some degree. The bad really overshadows the good when I look back though. In writing this I keep adding more bad things that I remember. I hadn't originally meant for this post to be focused on the negative qualities, but I guess that's what stuck with me. Overall it felt like an Uncharted clone by a developer with much less talent. So my post isn't all negative, I'll say the game did look quite nice. At least the first half did.
Spoilers sort of, not really though.
I agree with you about Trip. I was really hoping they were going to do something different and have Monkey kill her, but they just went with the boring generic love story. At least it wasn't too overbearing.
EDIT: The last poster reminded me that Ninja Theory is doing the DMC reboot. I had only played the demo for Heavenly Sword, which wasn't too bad. Now that I've played Enslaved I can see why people are so pissed. Now granted Enslaved was not meant to be DMC like combat, but it is pretty much the polar opposite of DMC 1/3. Slow, boring, and shallow combat with a bad framerate does not give a lot of hope for the new Devil May Cry.