What can I say about this game that has not already been said ...
It's taking up way too much of my life and runs like a dream and as for the ant lions do not get me started.
Have plagerised some reviews that sum up this game for me ...

"First and foremost, the graphics are truly an accomplishment. They're not as pretty in the "shiny/glossy" sense as Doom 3, but in the sense of creating the illusion of a living, breathing world, Half-Life 2 succeeds like no game before it. Particularly of note are the character facial expressions – they're so lifelike, they're borderline creepy! The characters move so realistically, it's like having CG actors in a video game, performing with every bit of emotion and skill as their flesh-and-blood counterparts. Equally impressive is Half-Life 2's physics engine. The gravity gun is easily the best new weapon in any FPS released in 2004. Whether throwing sawblades through a pack of headcrab zombies, or hurling an explosive barrel at a pack of Combine troops, the way Half-Life 2 implements the environment's many objects into gameplay never fails to impress".
" Half Life 2 concentrates heavily on a diverse amount of encounters with your enemies. Valve uses the tactic of presenting you with a "puzzle" and allowing you devise a strategy to solve it, and then just before you do solve it, shovelling crap into your face. They include numerous different feels to the environment, requiring a diverse mastery of strategies. While facing the Combine, you must carefully engage each enemy and find the best way to solve your problems. When up against the aforementioned sacs of crap, most strategic advantage is lost as they mindlessly advance on you. And talk about some awesome traps. While in Ravenholm, ammunition becomes scarce and you must resort to the saw (more on this later), and things like gas, flames, electricity, falling cars, a crazy preacher and the all-around life saver, the crowbar".

click any of these for a bigger picture and then go and buy it ...