I'll bullet point my thoughts and try to keep this brief
1. I don't see the point. So you're kind of in an open world, but it doesn't feel much like an open world. Not much is going on anywhere, it's just kind of empty and linear. I don't feel any urge to explore anywhere, instead the UI is just very in your face about everything. It will mark points on your map and mark out nearby 'events'. You're basically just running between instanced encounters.
2. The encounters themself feel relatively easy. It's a cover based shooter, so the peak of difficulty feels like rolling away from grenades and making sure you stay in cover, while landing headshots effectively. I can't see their being many interesting difficult enemies considering the setting.
3. The Dark Zone is basically the PvP zone in the division, but it also doesn't feel great. There's no real direction as per what you're supposed to do, and there's no real reason to attack other players. In fact, attacking other players is basically a death sentence unless you're in a large group. By attacking another player, you are marked as 'rogue'. Enemies see you on their minimap and are basically told 'kill this guy'. Within 30 seconds you'll be surrounded and dead.
4. The graphics are pretty decent and the framerate is good and everything feels and looks smooth. The UI is extremely bulky and awkward to navigate at times, but overall is relatively functional. The controls don't feel that great. This is clearly a console game, with physics based pivoting on movement, no jumping (space bar is used for cover, double tap for rolls), press CTRL to climb over things in a very slow and clunky manner, etc. The sticky cover feels somewhat decent compared to older renditions, but it still feels shitty as a general system. I found myself getting stuck in cover or moving awkwardly in ways I didn't want to because of the sticky covering.
For an open world game, I don't see the point. The PvE feels empty and generic, the PvP feels pointless. There's no reason to engage anyone in a fight. Maybe I just didn't play enough, but after an hour I wasn't left wanting to play anymore. I just didn't see reason to. Maybe I'm missing something and I'll be surprised when I hear more about the game. As it stands, I'm not going to get it on release.