Had a bit of a play with the Insider build - nothing heavy yet.
I notice that others have commented on the wide spacing of lines in File Explorer, but I had already adjusted that in a previous build. There's a proper setting under Options for it. MS assume that everyone is using touch devices and requires extra room for fat fingers.
If you pin applications to the Taskbar, they still get their recent documents shown on right-click. Those pinned to the Start Menu don't.
The size of the pinning area is fixed. Have more than 18 items, and a miniature scroll bar appears, in pale grey on white. The Suggested area also has a fixed size, being a list of recent filenames with relevant icons but without their folder names. Mine shows just the most recent 6 files used. There
is a "More" to show the same list as "Recent files" in File Explorer's Quick Access.
Clicking on the "All apps" button shows the stuff that used to be on the Win10 Start menu's left-hand column. Things on there get their Recent stuff.
There is a registry entry to get the Win10 Start menu back. Browse to "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" and create a DWORD called "Start_ShowClassicMode", then set it to 1.
Signing out then back in then gets me my pre-update Start menu, with all the pinned items in the places they were last week, and their Recent stuff intact. With the Taskbar alignment set to Left (in its Settings), things line up again and start making sense.
I still don't know why one PC gets Win11 and the other doesn't. Neither support any UEFI features, and System Information shows hardly any differences between the configs.