Officially now not the right forum, but I think most of us 2.9’ers look here first:
From the release notes
What’s new in 2.9.1:
*) fixed memory leak in torch tool;
*) fixed routing filter set-nexthop - was always setting to 0.0.0.1;
*) added VLAN support to tulip ethernet chips;
*) sped up IPsec AES decryption on RB500;
*) not running discovery protocol on interfaces that are in bridge
*) fixed bug - dial-on-demand interfaces did not remove dynamic addresses
sometimes;
*) fixed console bug - was crashing on scheduler scripts
*) fixed bug - DHCP server forgot dynamic BOOTP leases after reboot;
*) fixed atheros lock up under specific situations;