Doom is a great game graphically speaking for more than one reason

ive played it with 2 systems now first my beast (Athlon 64 3200+ (OC'd), GF6800 GT (Ocd to ultra speeds)) which runs at full everything... god its great

then for a short time i played it on my old video card (9600XT) and when set on medium detail and with no shadows the game still looks great

even on low settings the game looks great they did a real good job

as for the demo.... never tried it