Spearhead Formations are out!

The new expansion, Spearhead, is out, and in its infant stages:
http://www.games-workshop.com/gws/content/article.jsp?aId=9800021a

I immediately see three of the spearheads as useful to the Tau. In order of least usefulness to greatest, I'll give the explanation of why they are useful (in my eyes) and an example 500 point Spearhead:
-Skyfall Spearhead: Though there are problems with Deep Strike, the Skyfall allow the Tau to get into a good position mid-game, and they can slow infantry and wreck tanks. Railheads, would be ideal, as the blast would gain pinning and the Railgun would be near unstoppable. The Ion Cannon becomes more attractive due to the side armor rules. Smart Missile Systems would really come into their own here as well; Move 12" (Multitracker standard) fire the Rails at vehicles and the SMS at infantry entrenched in cover (no target lock needed). Possibly blow up three tanks and pin three squads on the deepstriking turn with the triple Hammerhead Spearhead.
Example Spearhead:
Skyfall Rule -45
Hammerhead w/ Railgun, SMS, Multitracker, D. Pod -175
Hammerhead w/ Ion Cannon, SMS, Multitracker, D. Pod -140
Hammerhead w/ Ion Cannon, SMS, Multitracker, D.Pod -140
500
This Spearhead relies on the multiple Pinning shots of cover-ignoring SMS and the Side armor rule to maintain a fast-moving, long-ranged war machine, capable of blasting away anything that relies on its front armor value.
- Seek and Destroy Spearhead: Would allow for a massed Piranha Squadron/ Gun Drone rush on a flank, with a melta threat of 30" once per game. That is an amazing threat, especially en masse.
Example Spearhead:
Seek and Destroy Rule -50
Piranha w/ Fusion Blaster, Targeting Array, Flechette Dischargers; Piranha w/ Fusion Blaster, Targeting Array -150
Piranha w/ Fusion Blaster, Targeting Array, Flechette Dischargers; Piranha w/ Fusion Blaster, Targeting Array -150
Piranha w/ Fusion Blaster, Targeting Array, Flechette Dischargers; Piranha w/ Fusion Blaster, Targeting Array -150
With the six Skimmers and twelve Drones provided here, you can harrass the enemy to hell and back. The strategy I'm thinking of is simple; the Piranhas rush forward as a long line, flat out and empty their Fusion Blasters into six seperate tanks. Mass panic from the enemy. Mass kills for you. Noticing the threat, the enemy will likely dedicate massive amounts of firepower to killing these squadrons; when the suprisingly durable vehicles remain, they will move at cruising speed and do so again, and again, all while dropping Drones to annoy and blocking the now dismounted and disarrayed enemy's movement. During this time, the rest of your army tears them to shreds.
Against hordes or footsloggers, the addition of Flechettes and the durability of the Piranhas gives you the luxury of simply corralling the enemy into a nice circle of Piranhas as you shoot them to hell. It is literally shooting fish in a barrel, in 40k form.
-Ambush Spearhead: THE best option for Tau. Three Hammerheads, all infiltrating to create an independent firebase of Ion Cannons or Railguns, deploying last (or at least after most) to gain side/rear armor shots. Not to mention that our vehicles get Stealth. This is huge. When equipped with Disruption Pods, our tanks get a 3+ cover save. This is amazing. Our vehicles have STORM SHIELDS. The tank goes from annoying to hard as nails. Diamond nails.
Example Spearhead:
Ambush rule -75
Hammerhead w/ Railgun, 2x Burst Cannons, Multitracker, Disruption Pod -165
Hammerhead w/ Railgun, 2x Burst Cannons Multitrackers, Disruption Pod -165
Hammerhead w/ Ion Cannon, 2x Burst Cannons, Multitracker, Disruption Pod -130
A cheaper version of the skyfall, as the SMS lacks the pinning sting, this unit can infiltrate in, with zero risk (unlike skyfall; thought of 500 points gone in a mishap = *shudder*), get side/rear armor, and proceed to pound the opponent.
There are three things that (in my opinion) make this Spearhead better for Tau in terms of the effect on the battlefield (even assuming that the deepstrike is successful). First is the 3+ cover. That makes this Spearhead impossibly durable to enemy shooting. The second is that the threat is there from turn one, as opposed to waiting for reserves. The third is that it has a psychological effect. If the enemy sees the Skyfall, they will continue on as is, expose rear-armour, than react after the turn they can come in; they can't stop the side armour shots, but you can't benefit from rear armour until the turn after. By then they react. With the Infiltration, the enemy has to deal with the threat of a flanked, near-invincible firebase, and that will have an effect on him. Does he dedicate units to it? Does he attempt to ignore it to hit your main army? Is he stuck in a side/rear armor crossfire between your real firebase and your Spearhead? You give the enemy the opportunity to make mistakes, to split forces, and you can capitalize on it.

What do you guys see as the potential of Spearhead formations? Any experience with them yet?