I have seen dozens of systems migrated from Gentoo to CentOS by live swapping the userspace and eventually rebooting into the new kernel. A hair raising experience to be sure.

DNS management. Think something like InfoBlox where I can have GUI driven control from simple adding a new zone record all the way up to full anycast configuration.

I love the terminal and CLIs to death but zone files suck and setting up bind or unbound/nsd is more painful than it should be.