If anyone is a Quake3 trickjumping fan, I wrote a small guide on the physics and trickability of Quake4. Here it is:
Physics in the single player game will feel very slow and tight similar to Doom 3 until you become a Strogg. As a human gravity is 1066 and speed is 160. Once you become a strogg, gravity becomes 800 and it feels very similar to Quake3 VQ3 physics. multiplayer physics are also 800 gravity.
Strafe angles seem to be close to the same, maybe a bit less (~28 degrees?). Halfbeat works. Rampjumps work. Stepups do not work by default so it is hard to go up stairs fast. You can enable stepup though with pm_step(up)size "8". Cannot turn with side keys like cpm.
Overbounces: Horizontal overbounces work. So far, vertical overbounces seem to be disabled.
Framerate: is capped at 60. The game will display that you are getting higher framerates than 60, but you are getting duplicate frames. 60 Is the cap. Framerates do no affect jump distances in quake 4.
Rocket jumping: is possible the knockback is very similar to Quake 3. 2x, 3x, 4x etc.
Grenade jumping: is possible the knockback is very similar to Quake 3. Jumping and then hitting fire right when you land with the Grenade Launcher will "stick" the grenade to the ground, no bouncing.
Hyperblaster climbing: the hyperblaster is the plasma gun of Q4. It gives less knockback than the plasmagun in Q3, but it is possible to climb with it. Hyperblaster hops give very little height increase.
Nailgun climbing: the nailgun in Q4 gives more knockback than the plasma gun in q3. You can nailgun up to a cieling and hold yourself up at the top indefinitely. You can also use the nailgun to gain speed as you "slide" across the ground. the catch with the nailgun though is that it has to spin for a second before it starts to fire. timing is important
Airstrafing: I don't know much about airstrafing yet. It appears that airstrafing does work, but it seems to be "tighter" than in quake3.
Ground friction: The ground friction is a bit different. Can't explain it. You can hold crouch and slide across the ground if you are moving at high speeds.
Jump pads: Doing a rocket+jumppad gives you much less height than in Q3. Grenades bounce off of jumppads