Looks like if I enable multiqueue-ethernet-default ie mq-fifo/pfifo on 1Gbit interfces, the system becomes completely unstable, interfaces flap, even total crashes/reboots. This is with Broadcom Netextreme NICs and Intel quad gbit NICs etc. They were ok on v6. The Intel 10Gbit 5xx series NICs are just fine. ...and copper 1/10Gbit SFPs actually seem to work fine in them.