Changes include ( comments in Italics are my own):

Client Fix: "App-V throws an error when the user selects the Preview button in InfoPath Designer." I wish that they would provide additional information of what the cause/fix was so that we would know if we see similar issues. But possibly this is due to special code that only affects virtualized office anyway.

Sequencer Fix: "The Sequencer does not correctly capture rapid creation or deletion of registry entries for applications with large registries". This fix is the first public fix for the sequencer since 5.1.  It covers an issue with an installer that we normally do not run into that was uncovered by a fellow MVP. As allways, the sequencer is only released as a full installer -- you never upgrade the sequencer. 

I assume, but have not confirmed, that the sequencer build includes the HF7 change to the sequencer that was only available in a private hotfix.

In spite of what it implies in the blog post detail, the standalone sequencer installer for the older operating systems IS included in the hotfix download.  You would only need to open a case with Microsoft to obtain the ADK Sequencer fix for Windows 10/2016, but presumably that version will become public soon enough with the Creators Build in April.

This hotfix is a direct download of the components that you are interested in, including other MDOP components.  No email required on this one!

Note: Windows 10 version 1607 and above, and Server 2016 and above, clients do not install these hotfixes as standalone installers any more.  The fixes would be applied to, and delivered by, operating system updates delivered via normal channels (e.g. "Windows Update").  Microsoft tells us that fixes should generally appear first in the 10/2016 branches before releasing the 5.1 branch; The client fix appears to be covered in the March non-security updates, while the sequencer fix would require a Microsoft Support Case (charges might apply?)  

NOTE:  App-V Hotfixes always include prior fixes on the same release.  In other words, you only need to apply the latest hotfix (5.1 HF8 in this case) and it includes other prior hotfices (5.1 HF1 through HF8 in this case).