Well, you case is different, it's second hand and cheap, but the guy I quoted just bought rMBP at full price, for that cost you' be able to get the new one in a week.
About the 1st gen thing... You (all of you) think there will be hardware problems? I'm gonna get it cause I need a new machine (I have an old Asus 4gb RAM, only works when connected and it's extremely sloooow. For heavy stuff I have the desktop PC, but I need a a laptop for mobility, so I can't wait any longer, and don't wanna spend money in some outdated machine right now.
Well, first gen rMBP had lag issues. Especially when using expose, mission control, etc. And it lasted for a couple of years (until Metal).
rMB has issues with keyboards. Keys get stuck easily.
And Apple is probably gonna use the same keyboard design for rMBP. I love the butterfly keyboard, got used to it in a day or so, and typing way faster on it then on this rMBP. Simply awesome keyboard if you give it a decent chance.
But the quality is so bad that it isn't worth to put it on a 200$ machine, let alone 1200$ machine.
The 2016 rMB didn't fix the issues, the keyboard problem is still there.
I am gonna especially watch out for keyboard in the next 12 months. If there are still issues, I will hold on to my 'old' rMBP for quite some time. If apple manages to fix the issues, well...