@sundogplanets @yvan I'd second the “whatever used thinkpad has the price you want to spend on a laptop”, with two caveats:
* I'm used to the european market, where used thinkpads are easily available at all price ranges
* my current “new and shiny” thinkpad is a T460, an upgrade from a X200 :D
but in my experience, and in the reported experience from a number of debian developers I know, thinkpads are pretty good workhorses, last a long time, they tend to work well under linux and once they hit the second hand market they tend to be good value for their price