Be careful when buying such products and be sure of what you are getting. For instance, Apple has an online store that offers "Apple Certified Refurbished -- We test and certify all Apple refurbished products and include a 1-year warranty. Limited supplies, but updated frequently. Availability is guaranteed upon receipt of full payment."
I have absolutely no problem buying such a product, since Apple stands behind their products and if you buy from their refurb store, you get a 1-year warranty.
I often look at what the popular website woot.com is offering (they sometimes offer up great deals). Woot was purchased by Amazon a year or two ago, so they've gotten larger and offer more stuff. But you can sometimes still find good deals there.
Recently, there was a deal on refurbished Samsung tablets. Here's what someone on a woot forum wrote:
Looks like these are refurbished by a 3rd party. If the work was done by Samsung, it would have been noted as "Factory Reconditioned". A "factory reconditioned" item was returned, inspected, and restored to fully working condition by the original manufacturer or a certified partner. And the original manufacturer stands behind it with a warranty. It's as close to new as you can get without technically being "new".
So -- if you are buying a refurb, it's probably best to buy it only if it is "factory reconditioned" or refurbished rather than done by a third party.