For what it is worth, recertified HDs have a crappy warranty (90 days). If they were really as reliable as new drives, they would come with a longer warranty.
As was mentioned, it is very hit or miss on what you get. I had 2 recertified drives fail on me in under 1 day, 1 failed at the 91 day mark, and 1 still working (110 days old).
Unless you get it for a really good price, factor in the cost of shipping the drive back for service, and then compare that price to a new drive price, and usually, you don't end up saving anything.
I saw newegg has a crap load of recertified HDs on "sale" now, and, IMO, just not worth it.