Huh, only part I had trouble with was the sort-of jumping puzzle in the watery room Spoiler where you have to flip the switch and electrify the whole place to get the door open... kept missing the platform and assumed it was just electrified too ... I ended up having to noclip out of there my first time through. The section they modified was difficult, but certainly not impossible. It was definitely easier the second time through, as I knew to gather all of the explosive barrels and whatnot by the elevator before I went and triggered the fight I thought the escort part was a bit too monotonous. It was different, but didn't really do it for me. I really loved it when Spoiler Alyx climbed up the building then covered me with the sniper rifle - that was also pretty different from the normal gameplay and gave a different sense of teamwork.