Unless you're handy on H/W issues (as miss configuration, jumper settings, cmos battery) keep away Refurb Mobos, is not the same as a refurb Phone, when someone returns a Mobo is due some issue either inherent to the MoBo (manufaturing deffects) or caused by them (miss configuration is the most common), so those Mobo even if you're lucky enough to get good ones you'll have to invest time (and patience) dealing with the issues that originated its return, or maybe are not returned HW but MOBOs which boxes where opened due acidents, or Mobo from some defective Batch.
Whatever unless you know what are you doing dont bet on refurbs Mobo.
No Problems with CPU, RAM, even HDD.
Ahh with CPUs keep away overclokeables ones (those with an "K" at end) usually have been abused and its silicon is fatigued, Also Xeon CPUs the used ones comes usually from Rendering Farms, where they use to run 24x7 at full load.