IPv6 is easy to remember, at least for addresses IT folks will be using a lot. Take loopback, commonly 127.0.0.1 (okay technically through 127.255.255.255, but people usually stick with that). IPv6 is even easier, ::1. And router configuration will get a whole lot easier.
We'll get used to it eventually, but it's gonna take a while. One of the biggest problems I see is address allocation. If we're not somewhat smart about how addresses are allocated, the vast majority of address space will be wasted (as is the case today already with IPv4).
What about gateways, DNS servers, your Exchange server, the Active Directory servers, your intranet server, etc...
These are all IP addresses that I can rattle off the top of my head after a day or two of troubleshooting. IPv6 will make that quite a bit more difficult. Not to say it should be a showstopper, but it is a consideration.