Using IP addresses directly is a bad practice in general, it introduced security risks in many scenarios.

SSL - usually cannot verify the cert, defeating the point of SSL SMB - windows will fail over to less secure ntlm auth instead of kerberos

If your using IP addresses instead of hostnames to reference machines, you're doing it wrong.

Also IPv6 is easier to remember in general... We have a single large IPv6 allocation (eg 2001:db8::/32), and everything sits under that in a logical layout. For legacy IP, we have several different allocations in different class A blocks (104.x, 66.x, 62.x etc) plus all the RFC1918 space used internally

Sure, but most places are not setup to using DHCP on servers or automated installs. So you will be typing in IP addresses through some kind of console to configure the machine in the first place and you will be typing in that IP address in the DNS system and when someone remotely fucks up the routing or IP config then you will be manually typing in lots of IP addresses to fix it.

If you have enough nodes to care and manually assign and at the same time don't automate deployment that sounds like an issue in general... and not with IPv6. You're likely to typo IPv4 just as well with enough entries.

Yep, but in my experience you have to manage about 2000+ machines before management will allow you to spend time on setting up deployment automation. So around the time you are setting multiple new machines a week.

I've done automatic deployment for 16. It was still totally worth it.

Of course it is, automation is very nice, I use it for the handful of machines I have my personal stuff on. I am just saying that from my days as a sysadmin it was usually a years long uphill battle to get approval for automating even minor things.