I don't think retina is a risk. Lag: use Webkit and update to 10.9. IR: take it in for a replacement. If you can buy it, I don't see why you wouldn't unless you need expandibility. Also, consider the 2.3, 8, 256 model for $1599 becase 16GB RAM probably is not necessary for your uses.
Good luck with the decision and feel free to PM me with any further questions.
Good luck with the decision and feel free to PM me with any further questions.