Played this on a blitz with 5 to 6 CTD's.
My impression is that it was good at the early parts, with all the differences they tried to do... an extra office here, semi-altered routes there, you get the crowbar later etc, but becomes "more of the same" later on despite these same little details, like adding more locked doors to an area. Towards the end the smaller routes were changed more (e.g. individual rooms in Lambda complex), while the bigger routes remained the same (e.g. room-to-room navigation in Lambda).
Staircase behaviour annoyed me. Got the hang of it with the use key but I still don't really like it. I also thought that some areas were too dark that I didn't know where I was supposed to go, until I actually noclipped and saw the route hidden in a dark corner (the part after you launch the rocket is one). At least they got creative with something that's irked me for a long time already: the AI's inability to climb ladders. (ELEVATOR SHAFT

)
Combat being harder in general caught me off-guard big time. MP5 spray drops nothing quickly enough, while both the RPG rocket and the Apache helicopter move so fast that I couldn't score clean hits without running out of ammo several times... if I didn't drop off the canyon first. Tau cannon charge is practically useless without the right mouse and surface combo. At least there's less traps and hazards. Idk, the facility portrayed in this mod gives me the illusion that it'd do better than the facility in the original game in terms of OSHA compliance, even if only a bit... ????

At least the .357 can knock-down most things with a well-placed single hit... early on, anyway.
y no xen XD
Entertained me long enough, compared to the long and boring boat ride in HL2 which is impossibly worse if for whatever reason, you don't have the air boat in front of you...