I have a knee lift on my new Bernina. I like it, and it is good for when I am pivoting around an applique, or to make an adjustment when FMQing, but I often forget to use it during things like chain piecing when I pick the foot up and put it down a lot.
I also have the problem of going for it, and then pressing the foot pedal at the same time: oops! (Driving with my left foot is not an option. I don't have enough brain coordination to do that! The speeds would be way too inconsistent to FMQ.)