TeamTNT got blown up.
Gameplay: Please, Read my Doom review. It contains everything you need. One thing I will say is the difficulty is significantly harder. It was made to be a challenged for the people who completed Doom II on hurt me plenty or higher. The level design is also different from id software's design.
Graphics: Same as Doom. Read the review.
Sound: The music is pretty darn good at least, and the title screen is great. This game has a good soundtrack.
Story: The story isn't really that different from original Doom, but they are both based on Doom II's events.
Value: These levels were supposed to be free but that isn't the case. But £5.99 is a good Steam deal, as always.
Verdict: Final Doom is good, old school Doom gameplay, but after Doom and Doom II, we didn't really need another old school Doom, but if we get it we should appreciate it. If you want more doom, buy it. If you are buying it because you want the complete doom series, don't.