It is my understanding that Glock-refurbished guns, while used, are inspected with any worn parts replaced -- and receive the same warranty as a new gun. I tried to get a definitive answer on this point, and see them advertized as "refurbished with NEW warranty", but nothing directly affirming that from Glock. (I may not have looked in the right places.)
If it is refurbished and comes with a new warranty, what's not to like? That gun is, for all intents and purposes, a new gun, Once you've shot your "new" Glock for a round or two, it's esesentially no better, unless it is a newer generation gun with some new features you want.