I used a Honda Accord with a similar system and even had a similar experience to scenario 1 on the interstate (though I was set at 69). After I realized that the following distance control was the reason the car was going slower, I was initially fine with it, but then someone cut me off which then forced me to driving slower resulting in me turning off the system.
I have a feeling these systems won't really be great until all cars are using them and considering I don't see that happening, I don't see them gaining a ton of traction, unfortunately.
My mistake. Yeah, people easing over from the left lane going slower than you or just in front of you is annoying. The only real way to combat this is to make them commit to going faster than you by speeding up, or going slower than you by keeping them boxed in. All in all, sounds possible like not great cruise conditions, which is pretty much all the time in most metro areas now.
I have a feeling these systems won't really be great until all cars are using them and considering I don't see that happening, I don't see them gaining a ton of traction, unfortunately.