One of the amazing things about the Tau Codex is the 5 point Disruption Pod vehicle upgrade. These wonderful little pods throw out visual and magnetic distortion to give your Tau skimmers a 4+ cover save from any shot fired from more than 12 inches away. This won't help you against Meltaguns, but keep your distance with your vehicles out front and you can layer your army to operate with a 4+ Cover on every unit, regardless of terrain!
Frequently in games, opponents find themselves cursing the dice-gods as I repeatedly roll 4s,5s and 6s as incoming lascannon, battlecannon, demolisher blasts just bounce off my Hammerheads. With the XV8s hiding behind the tanks, making pop-out attacks and moving back behind the tanks to claim cover saves, they too are finding their lifespans dramatically extended.
A word of caution however, keep your XV8s too close to your skimmers and blast templates can be positioned to the rear of your tank's hull, with the hole centered on the target vehicle and two XV8s caught in the blast. This is simply mitigated by holding your XV8s back at least 3 inches from the skimmer.
The Disruption Pod is one of those pieces of wargear that keeps the Tau a competitive. With tournament boards commonly laid out with sparse terrain, this gives us a huge advantage over other armies. This opens up the board for you. You can move where ever you want and still get the cover you need to keep your forces alive.