I also use and love Thinkpads as dedicated GNU/Linux machines. I have a T60 running Arch Linux, an X301 running Arch Linux, and a X30 running Debian. All work marvelously despite being >10 years old in some cases. I do Android development on the X301 which I upgraded to 8GB of RAM. My only gripe with any of my Thinkpads is that their processors are under-powered by modern standards but you won't notice unless you are compiling something large, running an emulator, or running something virtualized. The best part is the price, I paid 40USD for my X301 and have had no issues for years.