OK, here are my impressions after 2 days, 250 miles with AP 8.0 in highway as well as stop&go commute traffic:
1. Stop & Go traffic: AP is a lot smoother, more human-like driving. Definitely improved.
2. Highway traffic (+/- 70mph): no difference to 7.1 whatsoever. Still sways when losing one lane marking, still occasionally tries to follow cars when they exit.
3. Lane change: seems to work faster for me now compared to 7.1, the car seems to "think" less before it starts the maneuver.
4. The promised "turn signal detection" doesn't work. Ever. Had quite a number of scenarios today, and the car reacted as "surprised" as it did in 7.1 if a car cuts in, even with turn signal activated.
5. Lane change to exit: does not work. Ever. Tried a couple of times today, and it doesn't take the exit. Maybe it is better that way, since I am pretty sure that if it would work, the car would not start slowing down by itself... Which definitely defeats the purpose of this "feature".
6. See one car ahead: based on the display on the IC, it works fairly well for cars which are pretty close to the car directly in front of the Tesla. If there is a wider gap (I'd say more than maybe 20-30 feet), it doesn't seem to work (again, by judging the display). Thinking about it, I guess it makes sense - the angle for radar reflection gets more narrow the further the second car is from the first car, and hence the lower the probability of the Tesla radar catching a reflection back. I am not sure how effective it really is for AEB - it seems to allow for maybe another 20-30 feet of reaction time under ideal conditions. Certainly better than nothing, but it will never replace an alert driver being able to see ahead of the road.
7. Nags: subjective, but they seem to be more frequent. Nothing that gets me upset though.
Bottom line: I love the stop&go improvement (and that is big for me, as my commute consists of 75% of that traffic pattern). Other than that, there is not really a noticeable improvement compared to 7.1.