I wouldn't have an issue buying a used one as long as it looked to be in decent condition. I would want to make sure it was one of the newer superglides that have the plastic wear plates that only need a shot of wd40 type oil as opposed to the older grease or graphite spay lube models.
2006 Silverado 2500hd duramax 4x4 - with a few mods
I bought my super glide used. I used it for 2 years and it was great. I spent around $500 for the 18k and rails, found the bracket kit locally for free. Figure I saved over $1000 but I'd probably do it even if it was only $500 savings.
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010