I have the late 2013 Macbook 15" Retina. It's a nice machine.
I replaced the battery a few weeks ago. Well, ok, I paid Apple to do it. Not cheap but as they're too lazy to unglue the existing one they replace the entire top casing. So, new battery, new touchpad and new keyboard. Nice.
The only issue with it is the screen. I got it replaced around 3.5 years ago but "staingate" is causing issues around the edges again. It's only in the bezel area so has no impact on usage - it's just an aesthetic issue. I guess it'll get worse over time, but if it does there's always the "listerine" trick of last resort. Removing the anti-glare coating.