Refurbished doesn't mean something is wrong with it. Some times customers do return not because something is wrong, but they just changed their minds and don't want it (Lenovo may charge a restocking fee).
So while you might get one that was fixed for some problems, but you could also get a brand new untouched thinkpad. Of course, you will never know which one you got, but as long as your thinkpad has no problems, it's all good.