It’s funny that you ask. The organization I am working with that spawned this question in the first place has /22 dhcp pools at multiple sites-- for both VoIP and workstations. “For future growth…” they said. Why the decision was made not to scale with additional VLANs at a later date is beyond me(or my pay-grade).
They thought it was preposterous that I suggested that there are a lot of providers/networks that exclude .0 and .255 host addresses from DHCP pools/etc, and do not use them as a matter of convention/best practice. I casually suggested this fact and was subsequently chided.
The reason I posed this question in the first place, is that in my experience, most organizations I have worked with do not use them. It appears from the thread that there are some legitimate concerns with using .0 and .255 hosts, even though many consider these concerns dated or legacy.
Thanks to everyone for their opinions.