We had a 2004 Forest River Flagstaff bunkhouse model. It served us well when our two daughters were going with us. It seemed that age finally caught up with it and everything started to fail and I mean everything. Refrigerator, AC, hot water, floor needed replaced on the entire lower level, furnace and the finish was looking worn out. I repaired the frig with a new cooling unit but took ill and just couldn't keep up with everything else.
I had done considerable research and what I found in reading multiple forums and blogs etc. is that Grand Design does have issues like the others BUT they seem to stand behind their units a lot better than the others. We purchased a new 2017 GD Reflection 27RL last June and we love it. Only issue is latch on bathroom door needed adjusted and I have a small area of caulking that needs touched up and that has been it. One thing to note is GD has been bought by Winnebago. I do not know how this will impact the customer service as of yet.
Since you mention automatic leveling I will tell you I love it. We actually looked at a 2015 used GD 27RL and the new one. There was not a huge difference in price BUT the 2015 did not have auto leveling, convection oven skylight and a host of other small things. We went with the new mainly because of the auto leveling.
I agree with the other poster regarding the used unit should have all the kinks worked etc. BUT the flip side is that it could have issues that can not be fixed easily as well. If you do go the route of used make sure the dealer will stand behind the unit. I would insist on a shakedown right at the dealer making sure all systems are functional. HVAC plumbing frig jacks etc. If they are not willing to do this I would move on.
Good luck and I wish you well on whatever unit you choose!
Dave