UNMAP behavior in ESXi 5.5 P3/ESXi 6.0

I've had a few questions on how the VAAI UNMAP primitive has been changed in ESXi 5.5 P3 and ESXi 6 since I re-tweeted a colleague's blog post on it. The changes will be documented in my VAAI whitepaper but as I don't have a plan yet for publication, I wanted to include it here...