For those Tau generals who may be missing this little gem in the pile of new toys we recently got, I highly recommend taking a second and much harder look at how this Formation can affect you positively.
First, many who read here know that I am a General who values knowing and seeing what the enemy will do before committing. The intelligence I can gather via the various deployment shenanigans and ideas I have espoused in the past is priceless in value, especially for this reason: there is SO much new information to know and sometimes seeing their plan unfold a little bit is all you need to counter it, even if you're not incredibly familiar with their codex or formation and so on.
Newer players may find it extremely valuable to use this Formation for this reason. Another reason a newer player might want to use this formation is that the new wave of codex's has made Alpha striking (meaning armies that can charge turn one or make a severe impact in that turn for some reason or set of reasons) so much easier to do. Great examples of this are the Space Wolves, the Annihilation Formation for Space Marines, the new Psyker powers (again... Space Marines), Forge World models like the Lancer (more Imperium love) which posesses ridiculous speed or even more mundane examples like shunting DreadKnights. The White Scars have broken Space Marine Battle Companies.
With all this going on it would be the easiest of things to see a new player quickly grow uninterested in the hobby if they do not have some way to counter this. sheer firepower can carry you to some extent but canny enemies know that the number one rule for defeating Tau is to engage them in close combat and newer players need an edge against this brave new world.
Enter the Infiltration Cadre. It requires three units of Pathfinders, two units of Stealthsuits and a Pirahna. These are not universally accepted as the best units in the codex, clearly, and this alone could cause someones eyes to slide right over this page and onto the next one which shows the Optimized Stealth Cadre, their minds saying to them "if I want Stealth Suits, this is the better way to go". What they would be missing by thinking that is how this effectively negates the alpha strikers of the world.
Here is how I use it:
If an enemy wasn't going to kill your Piranha round 1, it stands to reason he won't round two. What would be the point of inviting the exact same thing if you weren't willing in round 1? The trouble is he knows that even if he doesn't kill it, some reserves are coming in. So he will likely be more disposed to killing it. This hurts the Tau Empire not at all. The only one who can win by the Piranha staying alive is the enemy! By keeping it alive, it could limit my reserves from coming in. Ironic.