I tested here alt+enter-switching a ntvdm-window(running commander keen 1)

                            when explorer.exe is running at alt+enter-switching time                   when explorer.exe is NOT running at alt+enter-switching time (aka explorer-killed earlier)

73331                       affected, alt often hung after alt+enter                                   affected, alt often hung after alt+enter
71322                       affected, alt often hung after alt+enter                                   (not tested)
68000                       affected, alt often hung after alt+enter                                   affected, alt often hung after alt+enter
66666                       affected, BSOD on first try to switch fullscreen after 2 exceptions        affected, alt often hung after alt+enter
                             ->not what I'd call better compared to trunk head

65495 (last explorer_old)   affected, alt often hung after alt+enter                                   (not tested)
64001                       affected, alt often hung after alt+enter                                   affected, alt often hung after alt+enter
56300                       (not tested, ntvdm must be invoked via console, I don't know how)          (not tested)