I've been running one of the nightlies for 1.2, most recently "vyos-999.201603162137-amd64.iso".
There seems to be a kernel default route that cannot be touched (UPDATE: kernel default route only exist when address is received via DHCP), even via a static route (kernel route precedence). This creates problem if a different default route needs to be set, for instance, using a different interface, or as the dhcp-interface option does not work due to this as well.
Further, wan load-balance does not work, and sends all traffic via the route as shown in the kernel default route (may be related).
If further clarification is required, I am happy to assist.