I purchased Doom 3 a couple weeks ago based largely on the overwhelmingly positive reviews online. I'd been somewhat skeptical regarding both the potential for the game and based on the problems with current reviewing practices (see post below).

My concerns can be summed up as follows:

• Early evidence showed that the game would only be playable on very high end current systems, and that possibly only future systems would be able to access the full potential of the game and it's engine.
• The engine itself, along with the high level of graphics, seemed to create an optimal environment for score inflation.
• The game was termed a "remake" or "reimagining" of Doom, which didn't need to be remade, since it is still one of the best games ever made (and IMHO better than Doom II).
• With the exception of a brief fling on the Dreamcast version of Quake 3: Arena (which I loved online), I hadn't enjoyed any of the id games produced after Doom II (although I played a port of Quake I on the Dreamcast as well, and that was adequate, if somewhat sterile).
• Return to Castle Wolfenstein was utter crap, playing off many of the worst aspects of current games (again, IMHO, maybe I should give it another chance).

• The engine -- it does produce quite spectacular visuals.
• But, the game does not highlight the engine -- it focuses on the game: storytelling and frantic action (as opposed to Quake I, which was basically a tech demo).
• NPC actions -- there are some really good examples of things popping out of the environment that either contribute to the atmosphere or clue you in on enemies, I'm thinking particularly about body parts churning out of ventilation shafts, and barrels or jugs being tossed down by imps, not to mention the first encounter with a pinky where it attempts to bash down the door.
• Background character story arcs -- essentially every character with the exception of a select handful (who also die quickly, for the most part) is not interacted with in a living state, however, they all have lives that are connected to the lives of other people on Mars or on Earth.
• Darkness -- Doom 3 puts a premium on light in the base, few areas have windows to let in "natural" world light, and the power systems have been terribly stressed by the activities in Delta Labs. Naturally, this means it's going to be pretty damn dark, which adds new actions and psychological reactions to gameplay: searching corners with a flashlight for items, tossing grenades into dark areas to provide temporary light and hopefully kill any lurkers, finally realizing that you don't have the flashlight in hell then feeling powerless (personally, I felt the absence of the flashlight far more severely than the loss of the major weapons systems).
• Online Co-op -- need I say more?

• Corpses disintegrate -- this may be a factor only relevant to the Xbox.
• The Shotgun is extremely powerful -- in fact, in many cases only one to two blasts from the SG will completely destroy anything up to a Revenant, which tends to make the other weapons more or less superfluous. Unload that sucker on a Hell Knight and it'll be left gasping for breath (before disintegrating of course).
• The Hell Knight redesign -- I was very disappointed by this, particularly since most of the enemies prior to that point were nearly pixel for pixel from the prior games. This seems to be yet another example of Doom 3 playing down the hell/Satanic imagery that marked the earlier games. Visually, the Hell Knights are now harder to identify as a threat outside of what is presented by an Imp.
• The sidelining of ritual imagery -- you find one area relatively early on where some sort of growth is taking over the base, and there are some ritual items in the area, but for the most part, this sort of activity has been sterilized from this remake (even though it is alluded to in emails).
• False alarm tricks -- when a floor tile pops up, and I can't sneak down under the floor, I'm disappointed. These tricks also seem to bring you out of the game for a moment. You're clearly in because you have a visceral reaction, but when you realize that the danger is not real either in the game or in real life, suddenly you're out of the game.
• Online Death Matches --- No dedicated server option, maximum 4 players per game, but in real life, without dedicated servers, you're lucky to get a lag free match with 2. In a game like Rainbow Six 3, you've got 8 players tossing one back on a routine basis...Unreal is far beyond that. Surely id could have done better than this. The extremely low number of people online playing is about all that you need to see to know that this isn't adequate.