Seems like the Alpha has ended. Some thoughts:
Snowdrop has really nice lit volumetrics and particle features, everything else is average.
Visually the biggest downgrades are in the diegetic UI which was such a huge part of the E3 2013 trailer, and which looking back were obviously all faked. There's no instances where you open a gun case and examine the gun loot inside with cool infographic overlays and stuff, for instance, and the holographic map is quite a bit less less dramatic. Streets don't all have their own diegetic floating name, you don't scan every dead person's face you come across and find out their life story, etc.
No sign of any of the procedural car destruction they showed off in the E3 2013 trailer. Bullet strikes on windows produce simple bullet-hole decals. Maybe in the PC build? I didn't see any instances of bullet penetration which they highlighted in 2013 as well (the guy getting scanned and then shot through cover, the bullet holes in the billboard actually letting sun-rays through). They do have the car door closing though, I know that would be a deal-breaker for some.
Controls are pretty clunky, noticable input lag on many movements and actions. Cover system is implemented and the game constantly hits you over the head with object highlight prompts to stick to cover but by the end of the alpha I abandoned the system completely; it just gets in your way.
Game has an unfortunate one-two combination of very spongy enemies with poor hit feedback. Games like Destiny that have excellent feedback on enemy hits can get away with spongy enemies (to a certain extent, at least). In it's current state the Division can't. It feels pretty ridiculous seeing some random thug absorb 50 bullets from a belt-fed LMG.
No passive matchmaking (IE: Destiny-style) in areas outside of the Dark Zone or the Hub home base, at least in the Alpha, which is disappointing. You can do a face-to-face team join with strangers in the Hub or Dark Zone with no loading screens though, which is cool. They've also implemented prox chat in the Dark Zone, which is cool.
Encounter pocket density in the "overworld" (non-mission-areas) is really, really low. In both the Dark Zone and the PVE-only areas you can walk for many minutes without seeing a hostile NPC. The Dark Zone suffers the most from this since there's no missions and seemingly no public event style occurances. In fact a lot of my Dark Zone time seemed to consist of groups and individuals wildly searching across the map for the elusive groups of enemies.
Willing to keep going with it into the beta and retail to see what else they've got up their sleeve!