WS:2 BS:3 S:3 T:3 W:1 I:2 A:1 Ld:7 Sv:4+
From what you can see above, I'm sure it's no surprise that Tau suck in melee. What they do excel at is ranged shooting. They cost 10 points a model as well, so you can easily get a good number of guns on the field.
Pulse Rifles: 30" range, S:5, AP:5, Rapid Fire
These guns are awesome, and at S:5, you have some ability to take out light vehicles (especially at rapid fire range). This is one of the two reasons Fire Warriors are awesome at shooting. The other reason is their ability to benefit from shooting at a unit tagged by a Markerlight. One of the benefits you can choose from a Markerlight is to have your Fire Warriors fire at +1 BS. BS:4 (with Marker Lights), 30" range, S:5, Rapid Fire? ...at 10 points/model? That's pretty hard-core.
For 10 points, you can upgrade one of your Fire Warriors to a Shas'ui (sergeant). He gets +1 Attack, +1 Leadership, and access to the Infantry Wargear list. The extra attack isn't worth it, but to have your squad benefit from a Ld: 8, as well as the capability of a drone/markerlight/etc. is probably worth the extra 10 points.
Photon Grenades: +1 point/model. These are defensive grenades, negating an assaulting enemy's charging bonus attack. I may get some flak for this, but I'm not convinced this upgrade is worth it. They suck in melee anyways, this just seems like postponing the inevitable. The benefit doesn't carry past the initial round of combat either, so it's not effective in the tarpit sense... I don't know. Assuming a 10-man squad, photon grenades cost 10 points. What else can I buy for that? A Markerlight for the Shas-ui. A bonding knife and a target lock...
EMP grenades: +3 points/model. These are used when assaulting vehicles. Roll a 4 or 5 to damage for a glancing hit, and a 6 for a penetrating hit. That flat out sucks for how expensive those are. 30 points? That's as expensive as an XV25 Stealthsuit!
OK, let's check out some non-standard upgrades only available if you upgrade a Fire Warrior to a Shas'ui...
Markerlight: You can equip your Shas'ui with a Markerlight for +10 points. That's not bad for how awesome Markerlights are. Only downside is that the squad that contains it cannot benefit from it. Only another squad can benefit from it (since it's not a Networked Markerlight).
Bonding Knife: 5 pts. Allows regrouping even if below half strength. For 5 points, I'd take this. The better the chances I can keep my guns operational and on the field, the better.
Blacksun Filter: 3pts. Awesome for nightfighting... which at the moment only applies during the first round of a Dawn Of War mission setup. Hopefully there will be more nightfighting in the new Missions book, and this piece of wargear will actually become useful.
Drone Controller: Free. Allows you to take one or two drones. You just pay for the drones you want.
Gun Drone: 10pts. BS2, Twin-linked Pulse Carbine. Pulse Carbines are 18" Assault 1 versions of the Fire Warrior's rifles. Twin-linked helps to offset the BS 2. Great for added fire at mid-close range and while mobile.Multi-Tracker: 5 pts. This would enable your Shas'ui to fire two weapons in one turn. An example would be if you bought him a Markerlight as well. He would now be able to fire both his Markerlight and his Pulse Rifle.
Marker Drone: 30pts. BS3 (due to an equipped Targetting Array), and a Networked Markerlight. The Networked Markerlight means the Fire Warrior unit it is attached to can benefit from the Markerlight.
Shield Drone: 15pts. It has a 4+ Invulnerable Save.
Target Lock: 5pts. Enables your Shas'ui to fire on a different target unit than the rest of the squad. Also useful if you have a markerlight.
One last option available to a Fire Warrior team is to replace all of their Pulse Rifles with Pulse Carbines for free. Pulse Carbines are 18" range, S:5, AP:5, Assault 1, Pinning. Again, I'm not totally convinced of the worth of this option. Pinning can be useful, but really only for enemies with low Ld. I do like the 18" Assault, though. This gives you a bit more range when on the move compared to the rifle (...though the full rifle gives you 2 shots at 12").
A unit of six carbine equipped firewarriors can be a useful 'sacrificial' unit when you want to rapid fire the assaulters to death. So few mini's mean your attacker is bound to succeed (which you want). The assault 18" weapon and the chance of pinning makes them just annoying enough to provoke the charge. (Suneokun of Pathfinder)
How to use your Fire Warriors
One method I've seen used often (though it's gone a bit out of favor due to the whole mechanized movement in 5th ed.) is the straight-up gunline. 12-man ,standard equipment, Shas'ui, Bonding Knife = 135 points. Put them in cover with a good lane of fire and fire away. 30" range is a big deal. If you have points to play with, give them a Marker Drone for added support.
Another great tactic/setup I've seen (and used) is 12-man, standard equipment, Shas'ui, Bonding Knife, Devilfish = 215 points. Mechanized and mobile, you are able to respond to threats easier. A great tactic I've seen used (lovingly called the "Fish of Fury") is to move your Devilfish up to ~3 or 4 inches in front of an enemy unit. Disembark your Fire Warriors (all exiting the rear access point, within 2" of the back. The Devilfish is 6" long and as a skimmer (as long as it's not wrecked or using it's landing gear) will not block line of sight. This puts your Fire Warriors in Rapid Fire range, as well as puts a vehicle in the way that (assuming the enemy would want to assault) will prevent them from getting into melee. They would have to go around the Devilfish.
While I like squads of 12, Suneokun prefers squads of 9. 12 isn't always the best, unless you are deploying in devilfish. 9 firewarriors will break after 3 deaths, the same as twelve. But 4x9 gives you four scoring units with decent firepower and the same breakpoints compared to 3x12. Plus 9 FW and a Shas'Ui are 100pt (makes the math easier). (Suneokun of Pathfinder)
Bryan prefers to use Kroot, so his Fire Warriors have a much smaller role on the field. FWs are ok...but i run mine as 6 man squads in a fish...they move around and contest and control objectives. (Bryan)
Any tactics or insights you have that I haven't covered? Drop in a comment and I'll add any viable comments to the review (with credit given)!