I also bailed somewhere around halfway through, though Black Mesa had me captivated the whole time (and I'm sure HL1 would've as well). I got to the point where you get a new ability (intentionally vague to not spoil anything), and you use that ability to get through enemy turrets.

I don't dislike it, but it definitely lost whatever I really liked about the first game, which I think is a sense of urgency or something for me. In the first game, I felt like I was constantly on the run, whereas the second has a lot of breaks in the action without a clear idea of the plan. I'm guessing it'll pick up soon, I just got a bit bored.

I'm guessing it has a solid story, but do far it's not quite as good as the first.