I have the 4TB versions, first batch. They had good firmware, were raid enhanced. We lost maybe 5 drives in 30 days, then have been stable since. We haven't had any fail in over 2 years.
This really depends on the batch they get and resell. The 2nd batch they got in from their supplier had bad firmware that they wouldn't even sell me.
I think the drives are RMA drives to the manufacturer, who sells them off to a refurbisher or disposal group, that then rebrands and checks them, wipes data, and sells. So you may get fixed drives which have a good chance of being just fine. Especially in the raid enhanced variety or NAS. For desktop drives, not so sure. The RE and NAS are more hardened so a refurb is probably still fine.