I bought my 2012 15" rMBP in December 2012 and it's still going strong. About six months after I bought it my screen developed image retention, but Apple replaced it with a nice Samsung screen. I haven't had it serviced since then and there have been no problems with it, but I don't take it out much as it is docked to my Thunderbolt Display (TBD) at home. The battery only has 140 cycles.
Since getting the rMB (2015 and now 2016) I've debated selling my rMBP as I use my rMB 90% of the time, but I have a weird setup that is only possible with my current machines. I also have a 2014 mini that I am using right now solely as a Steam streaming server with my eGPU. The TBD will only work with an eGPU via Optimus in Windows, so I could do this with my mini but I tried and lose about 30% in performance.
So I have the 15" rMBP hooked up to my TBD and stream Steam (wired connection) from the mini to it. This gives me better performance than the Optimus/TBD combination and allows me to game with my TBD, which I am rather fond of, but it requires two computers.
I know, this is a ridiculous setup and it is more logical to sell the rMBP and TBD, buy a new monitor, and then use the mini and eGPU with that new monitor for the best performance. I just haven't been able to find a monitor that I like as much as the TBD (IPS, integrated speakers, webcam, microphone, and a good design) so I'm keeping this setup for now.
Anyway, I've gotten way off topic. I've had my 2012 15" rMBP and, besides the image retention that was quickly resolved, I've had zero issues with it. It's been a fantastic computer for me after nearly four years.