Alright, I just HAD to give this a "3" in the features department.
First of all, with some CFG editing, I was able to get this running as fast as Doom 3 runs on my 1GHz MDD G4/1GB RAM/Radeon 9800Pro GPU. Please note that without that GPU I would NOT attempt to buy/run this game OR Doom 3!
Second, whether unfortunately or not, I had to compare this to Doom 3 as well as Quake 2 (from which the storyline continues). Insofar as the Quake series goes it's not that much more exciting than Quake 2 was on my old BlueG3 (which ran rather well with the Rage128 but better with a flashed Voodoo3 5500 PCI, albeit with banded lightmapping) but the graphics have been upgraded to take advantage of the latest technologies. This is where Features falls short: it's not memorably better than Quake 2 (especially with its online playability and awesome old MODs like Action Quake 2!) and Doom 3 does a much better job in setting the player in an environment where he/she feels that great attention has been paid to detail to the point where one may actually feel startled or frightened and otherwise enveloped in the gameâ€” Quake 4 falls a bit short of this. Sure there are things that you may see that may be described as looking technologically "awesome"... but I still feel a bit detached from the game.
That being said, I can't say I'm not having fun playing it. The weaponry is varied but you'll have a difficult time deciding which is really your favorite as there is not one that does/gives(?) that maximum amount of damage with a short amount of burst rounds where I might say; "Oh crap! THIS is my gun!" The rail gun proves difficult to aim and having to reload after just three shots is quite annoying where only a few guys may need to be liquidated and you spend half the time reloading.
The play is pretty linear, more or less like its predecessor (in storyline), and getting stuck trying to find my way to procede can be frustrating as I soon discover that I was supposed to be looking for some well-placed rabbit hole... err, vent. This was done in Doom 3 as well but the placing seemed to be a bit more intuitive with where one had to go...
Okay, I'll sum it up: if you like shooters and already have 'em all, get Quake 4. If you want to show off the graphic capabilities of your new system and already have Doom 3, UT 2004 and Halo, get Quake 4. If you just feel like it, get it... if you're tight on money this is NOT a must-get.
Out of five, if there was an Overall rating, I'd give this a 3 1/2.