I just got a batch of 4 new Raspberry Pis from Newark Electronics. Model B, REV 2 with the mounting holes. Silk screening on the back of the board includes "KCE MC1", "94V-0 F1", "07/02" and "13:01", "3A." I hope that is enough to establish that these are the very latest.
I copied an image of Arch Linux Arm from several months ago onto a new SDHC card. I think that image was from archlinuxarm-13-06-2012.img. It was configured on a REV 1 Pi with 256 MB RAM. I loaded it into one of my new Pis, plugged in the network and the power cable.
It wouldn't boot. It just sat there with a single red LED on solid, and no other LEDs lighting up at all.
I swapped around power supplies, prepared a second SDHC card with the same image; nothing, not on any of the 4 boards.
I took it to the location where I am using the earlier REV 1 boards, and verified that my newly prepared SDHC card works on the old board, and that the new board fails with an old, tested SDHC image of Arch Linux ARM.
All of this was consistent with a bad batch of boards. Then I tried one more test. I prepared an SDHC card with the latest Raspbian Wheezy image (2013-02-09) and it worked. All 4 of my new boards are fine.
So, apparently there is some difference between the older REV 1 boards and the newer REV 2 board such that the old version of Arch Linux ARM fails to boot on it. Is this a known condition?
I was hoping just to duplicate what I had done with the old boards, and Arch has even changed the way they handle start-up daemons, so that this means I will have to re-do some stuff.
Added: I have not yet tested whether the new OS boots on the old REV 1 boards. Those are in another building, so I'll have to make another trip over there.