I bought this for the XBox because I've decided to stomp all over my credit card debt before I blow $2k on a gaming machine. Pretty fun so far, but there are some annoyances too.
A lot of hay gets made about the physics engine. And when it's used well, it is a stunning piece of work indeed. Like, how you can carry a drum in front of you as a shield to deflect bullets. Neat stuff. I also love the ability to throw barrels of gasoline down slopes, watch them slide down next to an enemy, and them pop a few rounds into the barrel and make it blow up. Fun!
One thing that continually annoys me, though, is that the game engine seems to throw arbitrary limits at me with regards to handling objects and movement. See, I've gotten pretty good at piling stuff up in order to get over walls. First, I developed the ability to take stuff that had fallen over on its side and get it back upright. Usually by dropping it on something else in just the right way so it tumbles but lands upright. This, of course, is a stupid hoop - and a crutch for crap level design. In real life if I want a barrel upright, I just pick it up, move my hands 90 degrees, and put it back down upright. (Did that at least a hundred times when I worked at the plastic factory.) If your level design breaks when your players have this ability, then you suck as a level designer. Anyway, I'm quite good at it now, and can pile up just about anything (barrels, crates, cinder blocks, etc) at least three levels high if not higher. For instance, I got up to above the canal, where the enemies shoot at you from, and walked around in un-textured space up there. Kinda cool, actually. I also managed to take six cinder blocks out of the pit at the see-saw puzzle just before the "get chased by the helicopter" bit, and piled them up in such a way that I could have climbed up onto the walls around the sunken area. Could have - if the game engine didn't put an invisible ceiling an inch below the top of the wall!
The physics engine makes things in-game seem very realistic, and enhances my sense of immersion hugely. But when the metaphor suddenly breaks down completely, because the level designer wasn't thinking, my suspension of disbelief goes straight to hell in an instant. Don't give me a shiny new toy that's really, really fun and then go and snap the head off it just when I'm doing something cool! If you didn't have enough time or money to play-test, alright, fine. But you could have at least made the walls twice as high, so there's no chance of me getting close to the top no matter how many objects I pile up. Also, the fact that I can't climb over walls that are chest-high is absolutely ridiculous. Even with the HEV suit on, Gordon should be more than capable of grabbing a wall a bit higher than his head, pulling himself up, and climbing over. If I'm a huge nerd software engineer who's out of shape and at least 10 pounds overweight and I can do that, then so can "27 year old, MIT educated, highly athletic" Gordon Freeman and his sprint-speed-enhancing HEV suit.
Another extreme annoyance is that they scatter plastic milk crates capable of holding three med kits, two ammo boxes, several guns, etc, etc, around. But when you fill one up and try to carry it, it keeps tipping over IN YOUR HANDS and dumping its contents everywhere. Or when you walk over an bump on the ground, the stuff flys out everywhere as if you threw it all up in the air. Carrying more than one item thus becomes pretty much impossible, which seems entirely contrary to the idea of putting player-usable containers in the game. It's another example of how they don't seem to have a clue how a player would naturally want to use the capabilities of the physics engine.
The enemy AI is kinda sad. I suppose this could be because I'm playing on a 733 MHz processor and there aren't enough cycles to make the AI smart. Prime example of this would be how soldiers, knowing full well that I have a fully loaded machine gun (cuz I just wasted their buddy), will run through a door and then stop dead. They essentially put themselves in a perfect kill zone. I barely have to aim. It's just a matter of holding down the trigger until they all drop. And the machine gun spits bullets so fast, they fall almost instantly. (Guess their Combine-issue armor sucks. Not a big surprise.) Guys, you NEED a squad tactics advisor. Hell, you just need to stop and think for two seconds! There's a huge chest of grenades sitting right next to you. Shoot out the window and throw grenades at me all day! You're bound to get lucky sooner or later! (The HL2 website claims that "Neither friends nor enemies charge blindly into the fray." Well you totally could have fooled me!) Maybe this gets better later in the game...
Speaking of the machine guns spitting bullets fast... this game makes you wish soooo bad for a backpack. The pistol is actually fine. The magazine is 18 rounds (pre-ban Glock!!) and you can carry 150 exra rounds on top of that. I rarely run out of pistol ammo, even when I'm using it heavily. Each enemy drops 18 round magazines, though oddly ammo boxes for the pistol have only 20 rounds? The submachine gun, on the other hand, had 45 round magazines and as has been noted, throws bullets blindingly quick. You can only carry 225 spare rounds, which means you carry a max of 6 magazines, including the one in the gun. You eat through them like mad. You can also only carry five grenades at a time, which feels awfully pretty arbitrary - like the game developers couldn't make up their minds and just pulled 5 out of the air. To make up for not having enough ammo carrying capacity, ammo is scattered all over the place, and every single enemy drops it too. Which ironically just makes you wish even more for better carrying capacity! Especially since the level designers thought they were all clever by putting chest-high walls everywhere so that (they assumed) you can't go back to where you know there's still some ammo lying around. And as mentioned previously, you can't carry it around easily either. You're reduced to a "run and fetch" game ferrying around one ammo box at a time if you want to bring it with you. In my case, I know how to pile up barrels, so their sorry attempts to keep me from backtracking rarely work. But it's still an annoyance that need not be there.
I'm working my way through level 2, "Water Hazard" right now. This level makes you want a rifle - not even a scoped sniper rifle, just a medium-range weapon in general - in the worst way. As it is, I'm reduced to distance shooting with the pistol. The SMG is absolutely lousy at long range, which is quite appropriate. It's amusing to sit about 150 yards back from a guy with an SMG, taking careful aim at his head with the pistol, as he sprays with complete and utter futility in my general vicinity with his SMG. Generally he can go through two or three magazines and only hit me once. Hehehe. Another funny thing - when you run over a guy with your hover boat, you take 6 damage. That's kinda strange. I'd expect that if he stands there and lets me hit him (which they've done every time I've tried it), he's doing it so that he can pump bullets into me. But you're almost always moving far too fast to get hit when you're on the boat. So I should either lose no health in these situations (if he misses or runs) or a whole lot (if he shoots me three times in the chest point blank). It would also be slightly more realistic if at least some of the time they tried to dodge...
So, yeah, pretty mixed bag so far. I'll write again when I've finished it. I have a feeling that my irritation with the level design and dumb limitations on the physics engine aren't going to be abated, but maybe the rest of the game will be cool enough to displace that constant annoyance. So far the cut scenes are great, the friendly characters are cool, I love the engine... the levels just needed a lot more play testing, I think.