I'll need to play it to know for sure. There was a big focus on how "fast" it was, but the demo was pretty slow. Not even just compared to something like DooM 1/2, but as a FPS in general. Its really likely they slowed it down (not moving at max speed, going for every execution, etc) to make it easier to show off stuff though. Whether or not it'll be fast enough to call it a real successor to DooM 1/2 remains to be seen, though. I doubt it.
I also have my worries about the style of the levels. It's better than the shite that was Doom 3's level design, but is nothing close to how interesting the older Doom game's levels worked. I really hope we see less generic factory/refinery/whatever designs. Im tired of fighting in bottled up little hallways and squares spaces. The original DooM had outside levels that made the mars base feel way more open - hell, the first level starts with you overlooking a martian courtyard, while the second game places your back to a balcony to the outside. It opened it up, even if there wasn't much actual space in the game.
Sounds were a little lackluster. Yeah, the super shotty sounded badass. Thats good. The rocket launcher was really lame though, and so was the laser rifle. Seeing those huge laser rifle shots and the loud droning of the weapon was what made it feel so good - the quiet hum and tiny little laser bursts of the new laser rifle are really tame in comparison. Hope they get beefed up.