Spent the past couple of hours playing Doom 3 and below are my thoughts (will try to avoid plot/jumpy-bit spoilers but beware anyway)...
Firstly it both is and is not heir to the Doom heritage - for a start there's actually a story that makes sense and is explored, and as yet I've seen none of the massive dust-ups Doom was known for.. however certain tricks that were well know staples of Doom are present and correct here - so its kinda the same but different... WAY different...
Anyway, the game kicks off in much the same way as Half Life did - You're a new employee (this time a Marine) and you're a bit late, you've got a task to complete, which includes some tutorial stuff and gaining your basic equipment loadout and just at the end of your assignment we reach the fecal matter/circulatory device interface...
I'm not all that far into the game yet but thus far it plays more along the lines of a survival horror game rather than a straight shooter, however this suits the scenario of the game *extremely* well - its *extremely* good at ratchetting up the tension - and has some clever devices to help with this - for example the flashlight - lots of places are dark enough to force you to use it, however when you have the flashlight active you are limited to clubbing things with it - you can't have any other weapon selected at the same time - thus making you especially nervous about things jumping out at you...
Oh yeah, I mentioned similarites too didn't I - well OK firstly most of the old weapons are there (although I've only got the pistol, shotgun and machine gun atm) and also for all you old gits - do you remember what usually happened if you picked up a weapon laid out in plain sight in a well lit room? Well its already happened once to me since starting the game :)
Graphically the game is *stunning* - I'm running at 1280x1024, on the second highest graphics settings with 2x FSAA turned on and it runs flawlessly - what monsters I've run into are incredibly well designed too (thus far only Imps and Zombies, but hey, its a start :) )
So basically I'm not far into it yet, but I *really* like what I've seen so far - hope the rest of the game lives up to the potential thus far shown