I am running -current and since a few days ago (at least 2011/04/11) I am
unable to boot.
The boot process stops when it looks to find a bootable device. The prompt
(when pressing '?') does not display any device and yielding one second (or
more) to the kernel (by pressing '.') does not improve the situation.
A known working date is 2011/02/20.
I am running amd64 on a nVidia MCP51 chipset.
I am willing to help any way I can.
You could start from capturing and showing verbose dmesg. Full or at
least in parts related to disks.