[...] SQL Express fills roughly the same role for SQL Server
2005 & 2008 (though somewhat expanded, since it does allow
remote connections, which MSDE did not).
This is not entirely accurate. MSDE *did* allow remote connections.. The
main limitation in MSDE was that it only worked well with a maximum of 5
remote connections; if you opened more connections then it purposely
degraded its performance to discourage people from using it in this way (and
encourage upgrading to a "full" Sql Server). Sql Express does not have this
limitation and can accept an unrestricted number of remote connections.