In one way this is the worst of the Half Life franchise, but that said the Half Life series is one of my favourite ones and I still highly recommend this Episode.
You got nothing new from the moment you left your Buggy until the end of HL2 in this Episode, so a bit of "platform strategy" or vulgo "recycling" as we sadly know to well from other sequels, but still enjoyable.
There are not many new things, but the ones like the "Zombines" and flares are welcome and add well to the existing HL2 world.
Graphics are defo a step forward compared with HL2. As far as the story goes, this is really just a connection between HL2 and Episode 2 and nothing terribly new or exciting will be revealed, but by no means boring.
You got a bit of citadel and super gravity gun action, combined with a hint of Ravenholm in the dark, Sandtraps w/o pheromones and lots of City 17.