Sorry for forking this[1] thread (it's saved on my openbsd disk), but I'm having the same issues with booting the June 3 amd64 snapshot on my Thinkpad (T500). However, I'm not using softraid(4) on any of my disks (at least, I haven't changed any settings to explicitly use it).
I can grab a dmesg from bsd.rd if you want it. [1] http://marc.info/?l=openbsd-misc&m=130714931431027&w=2
