One of the few things I'd change about the X220 is the strange 2-piece lid. (What looks like a cosmetic flourish in the lid is actually a seam.)

Two of the four used X220 units I've bought arrived with the lid end piece wiggling, because it was no longer firmly attached to the main piece.

The X200 and almost every other ThinkPad managed just fine with a 1-piece lid, including being rugged against drops, so I don't know why the change.

I provisioned several hundred x220's for the school I was working at, figuring they were the most bomb-proof thing at the time. The lid section you're talking about was definitively not bomb-proof. Thankfully, it didn't make much difference to the operation of the laptop, but still pretty annoying.

The extra bit of the lid houses the antennas, it's plastic to not interfere with the signals as much as the magnesium would have. I do wish they could have attached it better or made the whole lid plastic over a magnesium frame or something.

The X220 touchpad and fan were pretty mediocre. The rest was outstanding, unless you didn't upgrade the panel. I hate nothing similar can be bought brand new.

Yup, also a problem with my X220/X230 units. My most recent repair attempt involves nails expoxied in internally, fingers crossed it holds. My previous repair (a carbon fibre strip glued on externally) failed after a drop.