Scripts with shebang should be chmoded 0755 by default when installed, wherever they are (unless, maybe, to /usr/share/doc). For example, scripts with shebang (#! /) (or #!/) put in /lib/udev or /usr/lib/ConsoleKit/run-seat.d should. Since a list of these places will be hard to come by, I think having a shebang should make you executable by default. Maybe this is for compat=8 only.