T420 - OK. Pretty durable and robust. Never took to the screen much; the keyboard seemed like heaven or hell depending on my mood; the trackpad was utterly terrible.
S400 - I like it a lot. Took a while to get used to the chicklet keyboard but like it now. Trackpad is good. Screen is fine. Very thin and not robust (screen can bend), and terrible battery life.
Yoga 11e - I quite like. Very robust, nice keyboard and trackpad. Crisp if small screen. Good battery. Screen can bend back but far too heavy to be a tablet replacement.
S400 - I like it a lot. Took a while to get used to the chicklet keyboard but like it now. Trackpad is good. Screen is fine. Very thin and not robust (screen can bend), and terrible battery life.
Yoga 11e - I quite like. Very robust, nice keyboard and trackpad. Crisp if small screen. Good battery. Screen can bend back but far too heavy to be a tablet replacement.