My understanding might be off, but a "refurb" is just a returned item that was checked out by the manufacturer and it passed the examination, OR, it was a faulty unit that was repaired.
My experience with refubs has been 100% positive. I think most are demos or sometimes customer returns due to insignificant issues like "I didn't like the color." Some have probably received an internal repair and then been repackaged for sale.
In many cases I have suspected that they were first quality goods that the manufacturer needed to move due to inventory being too high/optimistic production schedules or to clear out prior to a new model.
I just bought a pair of refurb binos:
ZEN ED2 7x36 Binoculars by Zen-Ray Optics that supposedly had "slight damage on the box." It was so slight I couldn't see it. I think they are moving an overstock. The "special deal" ended September 30, but I see that, Lazarus-like, it's now back, ending October 31. Another clue, IMHO, pointing to an overstock.
Interestingly, I ended up returning them because they were a little too big for me as a traveling bino. So they will again be sold, perfect box and all, as a refurb. (They are spectacular performers BTW if you are looking for good binos. Check out the birders' reviews.)
As someone already said, just make sure there is a good return policy. Then you really aren't risking much.