From someone that had to deal with the ghosting issue personally-- it does develop over time because when I first received my laptop, looking for imperfections was one of the first things I did and even after reading on the forums about the ghosting issues I couldn't replicate the ghosting with my rMBP. However, after several months the ghosting became more and more apparent and I eventually took my rMBP to get the panel replaced by a Samsung panel by the genius bar.
Like everyone else said, I'd keep an eye on it but I wouldn't worry about it unless you do start to see some ghosting. Keep in mind though that you have the full year on your warranty to take it in for any issues- IMO I'd check late into the warranty cycle (after 11 months of ownership or so), and if you don't notice any differences you should be good to go.
uhh, i ahve 2 retina macbooks atm
one was suppose to be a replacement for the 1st
iil try and keep this short and simple
1st one, has lg sja2 screen. its relly nice, i like how the white pops. but it made a crackling sound on the right speaker for the first 3 days, then it randomly stopped but by that time i called apple and they sent replacement
second one has samsung, woo, though white is a tny bit warmer but oh well.
though it was a tiny tiny nick and a scratch ont he back black plastic hinge.
which should i keep?