What's the advice on ULAs? On my internet-connected VLANs, I have a -er- site-local IPv4 subnet, a unique local IPv6 subnet, and a global IPv6 subnet. This works just fine.

Does the "advice" boil down to "You should NEVER use ULAs and ALWAYS use GUAs!" and is given by the same very, very loud subset of people who seemed to feel very strongly that IPv6 implementations should explicitly make it impossible to do NAT?