Executing files on double click can be very dangerous. For example, if somebody accidentally double clicks /sbin/killall5 all his programs will be shut down or even worse: as root the entire system will be killed. Also it can accidentally install evil malware!
Please add an option to the preferences dialog to disable executing all executables, so clumsy people like me can be safe.
PS: I think most people usually don't want to execute files on double click with a file browser, because their applications and scripts are in their menus or toolbars of the window manager or need additional parameters anyways.