The documentation here:
http://docs.unity3d.com/Documentation/ScriptReference/Input.GetJoystickNames.html

says that GetJoystickNames can be used to give descriptive names for gamepads instead of "Joystick 1", etc.

But (at least on Windows, where I've tested), there is no way to link a joystick's number for purposes of calls to Input.GetKey (Like Input.GetKey("joystick 1 button 5")) and setting up axes with its name's index in GetJoystickNames.

Because unplugging and replugging joysticks changes their number, and, their number can quickly become one that you don't have axes set up for, meaning you can't use the joystick.

There is no way to maintain a player's logical connection to a joystick across potential joystick unplugs/replugs.

What we need is for newly plugged-in gamepads to take the lowest unused joystick numbers instead of climbing progressively higher into as they are repeatedly unplugged/replugged. We need is something like:
static int[] Input.GetJoystickNumbers ();
which returns an array of numbers for joysticks that can be used by Input.GetKey for currently plugged in joysticks, where an index in this function's return value is for a joystick whose name is at the same index in the return value of Input.GetJoystickNames