Nice question!
I have a Juki TL98QE and a Bernina Activa 210. I use the knee lifter on both daily, open toe free motion foot, and quarter inch foot.
I do occasionally need a walking foot for binding, but that's the only thing I need it for. I recently purchased a high powered LED light for both machines, but unfortunately it's almost too bright - blinding - so I rarely turn it on.
I've also owned an Activa 240 and never once used all the extra stitches. It's really unnecessary!