I've played through roughly the first half of Half-Life 2: Episode 2, and boy, is it good. Not a question...
I'm going to keep this fairly short and as un-spoilery as possible, but I imagine most of the people reading this have completed the game already, so my caution is probably unnecessary. And I've already posted a whole load of spoiler-screenshots on my Flickr account. But anyhoo...
My impressions of Episode 2 so far, as numbered bullet points:
1) Ant Lions are even more annoying when they can spit acid.
2) Never try throwing explosive barrels at Hunters. Because they will shoot the barrel and blow you to bits.
3) Vortigaunts make good travelling companions.
4) Headcrab Zombies like toxic sludge.
5) Advisors are Brain Bugs from Starship Troopers. Except more scary. And psychic.
6) When all else fails, run the bastards over with the car.
7) An ammo cap of 18 rounds for the .357 Magnum is TOO SMALL.
8) The bridge seesaw puzzle is all kinds of cool.
9) Fast Headcrab Zombies don't like being hit in the face with a crowbar.
10) Poison Headcrabs still freak me out. Especially when they're being THROWN AT MY FACE.
More thoughts as I have them.