I didn't say the puzzles were difficult, I said they were terrible. Game physics were still in a very primitive state at the time, and to be honest, they just weren't very good.
Then again, I'm the type of person who can overlook a lot of things for a game with good set-piece moments and general atmosphere. I'm not going to pretend the AI wasn't as dumb as a brick or that the Vehicle sections weren't awful, but there's less than 10 single-player games I've played through more than once, and HL2's on the list. (Doing a Light-side then Dark-side run through the same game doesn't count because then I'm just riding through to see what I missed)
As for being on-topic, I'm pretty leery about this (and games of this type in general) because LoL seems to be the only one that doesn't rely on quasi-exploits like animation canceling and the like in order to stand a chance at ever winning a match. Fans of this genre seem to think that means it's competitive, but it just reeks of bad game design to me.