I played the MP for a few hours last night and here are some of my initial impressions:
This game is fairly fast paced, with nice weapons and graphics. It's basically Quake 3 upgraded to the Doom 3 engine, which is pretty much what I was expecting. I'm glad they brought the nailgun back, and oh how I have missed the railgun. Being a big time UT2k4 player, I really miss my dodging and the ability to boost my teammates across the map (instagib), but I think Quake 4 will keep me occupied until UT2k7 comes out.
There are a few things that really annoy me though, and I'm a little surprised nobody else has mentioned it. First, any time you make a change in the settings, you have to restart the entire game to get the settings to take effect. I guess this is the same as in Doom 3, but its just a pain to have to restart the game every time. Second, the gore effects are really poor. I always thought Quake 3 had great gore effects (and sounds), so every time you railed someone they exploded into a mass of bones and goo. Not in this game...I just don't get same satisfaction in Q4 when I frag someone. Third, the range of mouse sensitivity is terrible. At one point it is way too sensitive, and then the very next notch down forces you to slide the mouse across your entire desk to turn around. I'm gonna have to tweak with my windows mouse settings to see if I can figure out how to get mouse acceleration working. Finally, where are the RAIL servers!! I played on a dozen servers last night and didn't come across one rail only server. This was by far my favorite Q3 gametype (and UT for that matter) and I was dissapointed that I couldn't play this last night. I guess it is going to take some time for more servers to sprout up.
Anyways, it seems like I have more negatives than positives, but I'm just picky about my FPS' and will always be comparing anything new that comes along to UT. I think that with some new maps, better servers, and just a little more time to get used to the game, that Quake 4 will be one of my favorites.