I've owned the Ooma Core system for over four years without any problems. I'm happier with Ooma than I was paying for land line service and for me, it's completely free. Now you must pay a tax (usually $3.5/month) with the telo system which the original "core" system didn't have. I got my sister to buy a telo and my mother and both love it. No complaints. I can't speak about the refurb units, all of ours were purchased new.