I played pretty much the whole hour. Disconnected 4 times, but was easily able to get back in. The only time I saw other players was exactly at 6:00CST when it opened up, but it was basically just a mad sprint towards the FOB. After that I didn't see anyone else. As much of a big deal that people have made about the graphics, I have to say I agree. It definitely doesn't look great. It doesn't really feel or look like a current gen game.
The gameplay seems alright, but it doesn't feel as polished as other third person shooters like Uncharted or The Last of Us. I can see getting used to it, though.
There are lots of random NPC survivors stumbling around the streets. They don't react to being shot at or melee'd. They might get frightened when a gun is pointed at them, but they mostly feel like reactionless bots roaming around.
The enemies are pretty generic, but this is just the beginning of the game (the beta starts you at level 4.) They kept repeating the same lines.
Gotta say...this feels pretty meh. Not really surprised though.