I just read the statement of direction for the Oracle Database on Windows Vista.
As Application Express runs completely in the database, this implies that ApEx will get fully supported at the same time.
Below are the current plans for Windows Vista support for Oracle Database software:32 Bit Windows Vista (Vista Business, Ultimate and Enterprise Editions)
32-bit Oracle Database 10g Release 2
1st Quarter CY 2007
32-bit Oracle Database 11g
64 Bit Windows Vista for x64-based systems (Vista Business, Ultimate and Enterprise Editions)
64-bit Oracle Database 10g Release 2
2nd Half CY 2007
64-bit Oracle Database 11g