While the only major change to the Tau in Soulstorm from Dark Crusade is the addition of the Barracuda air fighter, this change is much more profound than might be initially apparent; unlike the new air fighters of many other factions which have been frowned upon by players as being very limited in usefulness, the Barracuda is a noteworthy exception especially for players who prefer the Kauyon build.
The Mont'Ka upgrade path still allows for the heavier combat units mainly aimed at stronger anti-vehicle and anti-building combat via the Hammerhead Gunship and XV8 Crisis Battlesuit (upgraded with a Rocket Launcher), but this does have a lower anti-infantry effectiveness and the above mentioned units might feel a bit "clumsy" to use, as they did in Dark Crusade. The Kauyon path from Dark Crusade was most definitely better at anti-infantry combat (among the best of any faction in the game) but their anti-vehicle combat was primarily limited to the Krootox and Skyray which were a bit clumsy to use as well.
The Barracuda has proven to be an excellent choice for anti-vehicle combat for a Kauyon Tau player. 5 can be built at full support. They can effortlessly get into position above your infantry to focus fire on key vehicle and building targets, therefore avoiding the major pathing issues that the Krootox and Skyray had getting through a sizeable Fire-Warrior army; they have VERY effective damage output against vehicles and buildings, and can easily in a pinch get over impassible terrain around defensive chokepoints to destroy key/vulnerable targets; and they can double as a quick defensive interceptor, rapidly repositioning against an enemy force attacking part of your base or listening posts which can be quite important for the Tau as they still don't have a standalone defense turret aside from listening posts.
On top of this, within the single player campaign of Soulstorm the Tau have it easier than most other races. Not only do they have their stronghold bonus of a cannon that softens the defenses of a territory before they attack, within a very small number of turns from the very start of the campaign they can get one of their legendary Elite Fire Warrior honorguard and then take over the Space Marine stronghold to get the Deep Strike ability, giving them absolutely excellent attacking strength on most territories. It won't take many more turns to get the remaining two Elite Fire Warrior honorguards, and having all three of these artillery-range anti-infantry death machines and the Deep Strike will make most known maps almost trivial.