Yes it is a shame that the AI isn't a little more realistic, especially when you are travelling on it. If I recall I heard someone from DTG (may have been Matt) that if it behaved in the same way as player services it would really hog resources. Whether there is a happy medium I don't know?
I think they should reduce the acceleration/deceleration a bit, as they throttle away from stations like it's about to explode. Other than that, i think the AI movements are pretty much on point.
Yes I think the 101 is too quick pulling away and you don't really hear the gearchanges which you would as a passenger. The others aren't too bad. It will be interested to see how a heavy freight train pulls away with the new NTP pack.
They had it enabled before. It wasnt too horrible. But think about it. Passenger trains are short. Why not have it enabled if you're on board?