My rMBP-15 was exactly a month old this week, when I found out that the thunderbolt ports were not working properly. I tested the ports using both the ethernet adapter and the VGA adapter (for overhead projection). The port closer to the Magsafe port would work occasionally, but the other thunderbolt port was not working at all - no ethernet and no video output. Took it to the Apple Store and they confirmed the problem. Since the repair would require replacing the main logic board, they graciously replaced the machine (even though it was past the 14 day return period). My bigger concern is that on the rMBP, the thunderbolt ports are machined incorrectly, and a rather loose fit results. The adapters in the rMBP do not fit as tightly and snugly as the VGA adapter fit in the display port of my old cMBP-13 (mid-2009). With my rMBP that failed, I was plugging in the thunderbolt ethernet adapter every day. Now, with the new replacement machine, I will try to avoid that. The fit is so loose that I am afraid this problem will happen again.