If it's an "Apple certified reconditioned product" sold only by Apple, it will look, feel and perform exactly as brand new. Anything not meeting that standard is replaced. Basically, a refurb is a handbuilt/overhauled machine made in Cupertino complete with a brand new serial number and complete warranty.
I'd prefer a refurb over a mass-produced in a Chinese factory new unit, since the factory defects are just far too common due to bad quality control. They probably inspect only a small percentage of the new machines that go out the door, and even those inspections are probably cursory at best. The refurbs are completely inspected, tested and made like new.