I found a problem in one of the 2 consoles I bought.
The main fan in the console didn?t sound normal. I had to get very close to hear it, like about 1 foot. I compared the sound to another console whose fan was running quieter and smoother, and the affected Xbox had a fan which sounded as of running slower, or as if you could hear the blades wobble, or as if it sounds like a sewing machine or some diesel engine, but like I said it was faint and only noticeable from a very close distance.
The sound of the power adapter of the affected console didn?t sound normal either. The adapter of the normal console had a faint smooth and steady sound (there is a fan inside the adapter as well, in case you don?t know), while the adapter of the affected console had a kind of interrupted or intermittent sound, although very faint as well and only heard from a very close distance of about 1 foot.
However, the affected console seemed to work flawlessly, though, unlike the non-affected console which froze on the initial setup screen (pressing A) and had me restart it, and then later giving me a blank screen while creating my gamerpic from my avatar, forcing me to do a hard restart (power+eject buttons).
I had to return one of the consoles, and I ended returning the one with the unusual fan sound. Probably an electrical or mechanical glitch, which I think is more serious. I am working on the other console now and will do a factory reset and monitor how fast it?s compared to the other one.
Both consoles had no problem applying the Day One patch, with the disk drive running smoothly as well.