I'm a pauper, which means I can only play games, in most cases, a while after they come out. It's a pain trying to stay current on modern gaming trends but I do what I can. It does mean I avoid the hype-cycle of the gaming press. It means I'm waiting to play some absolute gems: Bioshock for example, and Portal.
I also get motion sickness from playing first-person shooters. An hour is the most I can stand, before I feel sick. It's worse with more modern games. It pushes the FPS way down the list, and I pick and choose the ones I play carefully because I don't get to play many. As a consequence, Portal will squeeze my head like a lemon.
Still, I'm excited to play it, and the rest of the Orange Box, as soon as I finish HL2: Episode One.
Alyx is the big addition: she follows you, generally pouring lead into everything you see. (An amazing section in darkness gives you responsibility for what she sees, using your flashlight.) With her unlimited ammo, apparently recharging health and zombie-stopping melee attacks, she can look after herself. (It is possible for her to die, but not easily.)
It's good to have an escort that doesn't blunder about like an escort, but she's so powerful that you're better off luring enemies to her. It's an interesting change, but too often you don't fire at enemies because she can deal with them without an ammo cost. Balancing your use of different weapons so you don't run out of anything critical was a good feature of the series, and this undercuts it. Also, later in the game she picks up a shotgun. Why doesn't she take any of the extra weapons you find before then?
Despite that, I like her a lot. Her AI is good. She doesn't get stuck in doorways, nor does she get left behind, and she gets involved where she can without doing anything stupid. You never have to hold her hand, nor let her hold yours. She doesn't steal ammo and health pick-ups (The "Chaos Engine" maneuvre). She doesn't grate, even when she makes a wisecrack or too.
Other than that, it's a largely competent extension of HL2, and doesn't do anything radical. It feels like an expansion pack, which it is I suppose. There are several good set-pieces, although nothing quite matching HL2, and it delivers peril and plot points at a fair old clip. It shows a need to break out of City 17 (which Episode Two does).
I'm perhaps three-quarters of the way through it, and I've enjoyed it almost as much as HL2, which was the best thing I'd played in years. Once Episode One finished I'll buy the Orange Box and crack on with Episode Two. Portal can wait a little longer, for my brain's sake.