So I have 3 experiences with refurbished from Apple:
1. iMac - looked brand new, not one scratch or any indication of use but it failed to boot when plugged in. It was a 2012 iMac and when I took it into the Apple Store they swapped it with the newly released (at the time) 2013 iMac at no charge. I was in and out in 10 minutes, still using it today - no regrets (other than wishing I went with SSD at the time)
2. iPod Touch - this actually was for someone else but no issues and arrived looking brand new
3. MacBook Pro Retina (2015) - Purchased the top end with DG in February this year, came in a nice sealed box, again looked brand new, battery cycle count was 1, benchmark scores surpassed the average for my particular model. No issues so far. Read/write of the flash storage seemed to surpass the tests I was seeing on youtube. Best mac I have owned.
Apple Refurbished Store service in my few experiences has been exceptionally fast as well, usually shipping same day and delivery within 2 days.
I would say go for it. If you are not satisfied for whatever reason, you always have the 14 days to return it for any reason and refurbished have the same 1 year warranty + extendable AppleCare as new macs