A Quake 4 thread... damn, being the id-fanboy that I am, this means I'll be forced to post!
Anyway, I got the game on Thursday, I'm about halfway through the single-player (I think). It is, in a word, hardcore. Seriously, this game rapes Doom 3 so hard it's not even funny. And this is coming from someone who actually enjoyed Doom 3.
The weapons are fantastic (<3 the nailgun, the grenade launcher and hyperblaster, as well the dark matter gun). Most of your weapons will also get upgrades over time, such as an increased rate of fire or larger clip sizes.
I feel it bears mentioning that the dark matter gun is one of the coolest weapons in any game, ever. Essentially, it fires a huge black hole that sucks any enemies and moveable objects in the environment towards it before exploding and hurling everything away. Needless to say, this looks very, very cool.
The really big outdoor areas are noticeably underdetailed, but these areas are few and far between. The interior areas, as expected, have a unholy amount of detail. Most of the levels are lit well enough, though some are still dim, and a few are pitch black. Fear not! The machine gun has an attached flashlight, and your sqaudmates' weapons also have flashlights - in fact, the light beams shining from their weapons in darkened areas is one of the most impressive effects in the game (along with firing the dark matter gun).
Speaking of squadmates - unlike Doom 3, you're rarely alone in Quake 4 (at least up to the point I've played). Their AI is pretty good, and later on in the tougher levels, I've found their help is invaluable, especially since medics will restore your health and engineers your armor.
There are two vehicles, the hovertank and walker. I didn't particularly enjoy the hovertank sequence, but the walker is fun. And if you happen to not enjoy the vehicles, you can rest easy knowing that the sequences are at least short and fairly easy, as your vehicle's armor will regenerate over time.
There are some very memorable scripted sequences, such as the introduction of your sqaud's sniper, and later on in the game when your sqaud gets attacked by a Harvester.
Btw, Harvesters > everything
I'll post some screens later.
Holy crap that was long.
I bet you think that's funny, don't you.