Okay, so I posted my impressions based on 90 minutes Xbox One yesterday. Back today after another three hours.
It has grown on me. The game has atmosphere - it's paranoid and oppressive, even through to the music, weather etc. This is not a "HEY EVERYTHING IS AWESOME!" open world game. There's lots of humour in the hacked messages and such you will see - but the main story is played straight, and it's depressing.
While the graphics, to be honest, look bad last gen some of the time, as you get into it there's moments of it looking stunning. I just finished unlocking a ctOS station in the game (which took over half an hour and was not easy at all, by the way) and it started to both fog up and thunder during this. For those 30 minutes, it looked and played incredible. It was more stealthy than, well, Thief.
Also, the unlocks are great.
Downsides: the map isn't massive (I saw somebody superimposed the Watch Dogs map with GTA 5 map online... well, it isn't to scale properly as Watch Dog isn't GTA 5 sized at all). Also - minor bugs sometimes challenge immersion. I saw a dude NPC randomly fall into the water and immediately disappear. I also saw a car 'lagging' earlier - a computer controlled one rubber banding around the place. It was hilarious and weird.
Overall I'm much more positive after spending some time in the world.