My car has the current-edition Toyota/Lexus system. First of all, it's worth saying there're a whole slew of ancillary safety systems beyond the 'nominal case driving' automation, like rear-crossing detection, collision brake assistance, blindspot warning and so on.
For the self-driving stuff, I really only use the radar cruise control. The car does have lane self-centering but it's not great at detecting lane boundaries, especially when in bad weather or when there's a lot of traffic.
I have that system turned to an advisory mode so it'll beep if I start moving across a lane boundary without a turn signal on.
The radar cruise control is very solid. My only real complaint about it is that it leaves a large gap at low speed; even when in its tightest-follow mode. You can end up getting people merging in front of you, which then causes it to generate an even larger gap. It will take off from a stop, but if it's a long stop it wants you to hit a resume button.
I understand how the systems work at this point, they don't surprise me, and they help with fatigue. I'm generally an attentive driver (I know, we all say that) so I'm OK with the limitations. I don't really want any more.
Very anecdotally, the last time I tried a lane-following system (an Audi rental about two years ago), it tried to kill me by following the off-ramp into a gas station at 65mph.