So the rules for the upcoming Tau Ghostkeel Battlesuit have leaked, and it has a bit of a rules algebra that could be interesting, but is pretty cool overall.
Now, I referenced a rules question earlier, and that's basically just how the Stealth Field rule works. Basically, it says that a unit including the drone gains the Stealth special rule, and if it has the Stealth Special rule already, will replace it with Shrouded.
From what we can see, this seems to mean that the unit will gain Stealth and Shrouded. This is because the Suits's native Stealth is replaced with Shrouded, while the Drones gain Stealth.
The suits will also double their Stealth and Shrouded for shooting beyond 12", to a 2+, however, the Drones will not benefit and sit at a 4+ cover save instead.
The final bit of tech that seems really cool is Holophoton Countermeasures, which allows the unit once per game, in the enemy shooting phase, to force the firing unit, after having been declared as a target, to snap shoot. EDIT: Russel pointed out that this is actually per model, so a unit of several battlesuits can do this more than once a game. Even cooler.
Between this and the cover rules, this really forces the counter-attack on this unit to need to be a plinking away rather than a single huge salvo. On the other hand, the mandatory drones are a weak point, as killing off the drones is much easier than the suits and will force leadership checks, though at base leadership 9, that's not a huge weakness.
As far as output, the weaponry is a little lackluster in my opinion. It's not bad, but doesn't have the volume as some other units Tau can field. One consideration could be what the "Fire Team" special rule confers, as I believe that looks like a new special rule.
In the end, for 130 points, it's a pretty solid package, and a very cool kit.