I have several thinkpads (5) and run them all on Linux. Agree that the battery life is not optimal, even with TLP. Keyboards are typically excellent, but the brand of the keyboard can matter a lot (there are usually 2-3 different manufacturers of Thinkpad keyboards and they don't feel the same). Maintaining Thinkpads is usually a pure joy: super easy to open up, easy to replace RAM, sometimes CPU (depending on the model) and storage. And they are robust (will survive a fall).

Software wise, apart from some rare exceptions (X1 Gen 7?) everything works out of the box on most distros.