Safe to say It's the "weakest" part of the Half Life 1 series. It's still great, however! I loved the stages (even though they became a traumatic memory in my head, given im not the best and i played on Hard mode) and although there was no new weaponry to mess around with like in Opposing Force, i didnt find new weapons a must-be so theres that. The only part that I'd consider a bit weak is once you find the npc you were searching for and had to escort him back through a few levels. Luckily, they made a shorter path for that.
Aaaand I think that's all I have to say on it.