In most cases, 'refurbished' gear is pretty good. Actually, sometimes it's better than what you get off the shelf.
When things are being made on the assembly line, they go through Quality Control (QC) and if they fail a test, they get pulled off the line. The item is then inspected and probably fixed by hand and fully tested. It cannot go back onto the assembly line, so must then be sold as refurbished. So you get an item that is not only brand new, but has been fully inspected and tested.
Of course, refurbished could also mean that the items have been purchased and returned...essentially 'used'. But when something is 'factory refurbished', it probably goes through the same inspection and testing, so you are very likely to get the item in perfect working order.
I don't have any experience with Canon refurbished gear...but I wouldn't hesitate to go that route.