The biggest tangible benefit is you don't need to worry about NAT port mapping any more. Every device can have a public address, and you can have multiple servers exposing services on the same port without a conflict.

(The flip side is having a network-level firewall is more important than ever.)

You also don't have to worry about running a DHCP server anymore, at least on small networks. The simplicity of SLAAC is a breath of fresh air, and removes DHCP as a single point of failure for a network.