On halt/reboot umount local filesystems fails with newer kernels and will drop me to a root shell.
Could you please set (in Kernel Config) CONFIG_HOTPLUG_PCI=m (build as a module instead of "=y"). I suspect this to be the source of the problem on my Eee Pc.

This is now fixed (switch to devtmpfs was the issue, not CONFIG_HOTPLUG_PCI).