Disable automatic menubar icon sorting in Mavericks?
There are two types of menubar items in OS X. The classical one of type NSMenuExtra which is primarily used by Apple's own stuff like the clock, AirPort, TimeMachine, VPN and keychain, etc. These are not officially available for third party developers.
The other type is an NSStatusItem which is available for everyone and almost all apps that provide a menu bar item use this type.

Historically only NSMenuExtras could be sorted by ⌘ (command) dragging them and NSStatusItems were displayed in launch order from right to left. Since Mavericks Apple allow all items to be reordered by command-dragging them.

The chosen order should be persistent across logins. Some items like location services or screen synchronization will only show up when needed so they may change your sort order temporarily. The order is the same for all menu bars if you're using multiple screens.