This is, overall, a very good laptop that is unfortunately let down by an unfathomable design choice on the part of Lenovo.
As noted in the review, the bottom panel is incredibly thin, and therefore very flexible. That, in itself, is not a problem - what IS a problem, is that the ultra-thin bottom panel is only secured at the edges - there are no screws holding it in place in the middle of the laptop.
As long as the machine is cool, everything looks and feels okay. However, once it's warmed up, the bottom panel becomes even more flexible (I suspect that the thermal pads on the inside of the panel become softer) and starts producing very audible creaks, when pressed in the center. Even picking it up with one hand underneath produces this very obvious, very annoying creaking...
It boggles the mind how such an obvious design defect found it's way into production.