I took my essentially brand new MBA to an Apple Store in Calgary. I demonstrated the problem (hit a couple of keys right after the screen goes black). The tech proceeded to boot the machine off the network with a "known good OS", and the problem persisted. They kept it to run diagnostics overnight, then told me the next day that because the laptop passes the diagnostics, there is no problem. I had to chuckle at the Kafkaesque nature of their position ... it doesn't matter that I can demonstrate it - there is no problem because it passes the diagnostics.
As I tried to explain the absurdity of their position, I was told that if I want to do something else, then the next step would be to erase the HD, and do a full reinstall. I asked how erasing of the HD could possibly provide any further information, given that the tech had already booted the machine off their network with a known good OS ... and didn't really get a reply.
The point is that if I, and apparently other people can reliably reproduce the problem, then the techs at the Apple store should be able to locate it in their database of known issues, and not put customers through unnecessary hassle of leaving and picking up the machine, not to mention wiping the HD clean.
The famous "out of the box" Apple experience failed to materialize for me (my first black screen happened about 10 minutes after unboxing). The staff at the Apple store didn't help much either. I do have multiple other Apple devices - iPhones, iPads, Apple TVs, etc., but this is the first laptop. I'm having second thoughts about the MacBook Pro I have on order at work ...
I'm picking up the laptop tonight. Maybe the face-to-face conversation will be better than the one I had over the phone.