Virtual army-wide BS 4+ meaning the so-called "Ranged experts" of the galaxy are only as good as your off the line Imperial grunt without markerlight support.
And there's not much help until the codex comes out, which at this pace will be in 2023. Bad as in "does not have the tools to play 9th edition" bad.
Now that Marines are getting sloppy BJ's from Games Workshop every 3 minutes, you're no longer the most-hated faction!.
The glottal stop of everyone trying to pronounce your new apostrophe.
Miss the old days where the T'au was a highly mobile army? Congrats! New rules mean only infantry suffer -1 to hit for moving and firing heavy weapons.
You have a lot of advantages in Cities of Death.
Crisis/Commander suit weapons are Assault, letting them Advance and still shoot.
You have a wide selection of decent AP weapons.
A plethora of sources for wound-transferring mechanics including wound ignore rolls, and invulnerable saves can make your important units very resilient.
Easy access to rerolls on 1s to hit makes Overcharging Ion weapons much less risky than usual.
Almost everything bigger than INFANTRY has the FLY keyword.
Markerlights let you focus down single big targets effectively with your entire army.
You can pump out a lot of mortal wounds if you build around Destroyer Missiles and Rail weapons.
Strength 5 guns everywhere means your troops have an easier time wounding most MEQ things and T8 tanks/monsters.
The new codex basically turned Tau into Imperial Guard armed with Eldar-grade equipment - it's practically suicide to charge a Tau gunline.
Noteworthily, basic overwatch, like in 8th edition, can be performed multiple times, but using this special rule makes you unable to fire more this turn.
You can shoot overwatch with any unit within 6" of the charged unit.
Just stay the fuck out of melee if you don't want to be tabled for your own 'for the greater good' shitheads sakes. Because you like shooting and battlemechs, and being an optimist in a crapsack universe.