Very well.
I have just tested the feature, and it _does_ work, in fact making the sentry command far more useful than it was before.
First why to use it? Lets see.
I bet many here have played Civ of any Version, there was a similar command there - "sleep/sentry/board next ship".
The ship with the order sits in its place and does not list in the "next ship" window.
Once a no-treaty/enemy ship enters the system with the ship, the sentry command will clear out and the next one in the list will be executed.
I didnt know that before. Still i was using the order a lot. Useful for those border guard/outlook ships. just hit the next ship button and if the ship had encountered enemy it would appear in the list.
Another thing is using it for mining ships - send it on sentry to the mining field, after the sentry order give it order to go to refuel and then to go back. then give it order to go back. repeat orders.
Thus you will never need again to take care of the miners.
Now to the point.
Sentry order can be used a lot in scenario creation.
For example, if any empire enters X system, then the Y empire's no-support mighty full tech etc.etc. ships would go to specific point, say your homeworld
. You kill them, you win the game.
Could be nasty if there are, say four fleets of dreadnought and sun destroyers heading towards your starting systems.
Or another example, put a colony ship on sentry in a storm or group of storms.
Then just wait untill someone [the player] reaches the system. Once he does, the no-maintance colony ship will head to next order - zolonize Z planet. That'll start a new race, say the Monsters.
Just two i can think of right now. sure there are more options.
Just want to see good scenarios