The Armored Task Force is a large but flexible Formation. It includes a Techmarine, 0-3 units of Thunderfire Cannons, 3-5 units of Vindicators, Predators, or Whirlwinds, and 0-1 Sergeant Chronus. It's the only way to add Thunderfires and most of these tanks to a Gladius Strike Force, though it can be made large enough to be an army in its own right. Unfortunately, you can't just drop in a tank or a Thunderfire to a Gladius Strike Force.
By way of recompense, the Formation has Paregoric Chant, allowing vehicles to ignore Crew Stunned and Crew Shaken as long as they're within 6" of a Techmarine or Techmarine Gunner in the Formation. This is a great ability for Predators and Whirlwinds since they can stay in the backfield with the Thunderfires and maintain their fire. Vindicators need to advance and so will find this ability less useful. In addition, The Will of the Omnissiah gives the Techamarines +1 on their rolls to repair vehicles in in the Formation. Again, this will keep your Whirlwinds and Predators on the table since they can stay near the Techmarines.
When it comes down to it, this is an extremely fluffy themed Formation, and should be taken as such. The advantages it grants aren't huge and many of the units included aren't the most competitive. However, it's the only way to add Thunderfires, Vindicators, and Predators into a Gladius Strike Force, and is a decent addition if you have the points. The most unique use is definitely taking it as an entire army (the Armored Task Force can easily break 3,000 points). For the first time, Space Marines can field an armored company. I'm not sure if the tanks are strong enough to be a competitive army on their own, but it would certainly be a unique and fun army to play.
The Suppression Force is composed of a unit of Whirlwinds containing at least two and a unit of Land Speeders. The Formation gains Datalink Telemetry, which allows a Land Speeder to nominate a unit within 18" (as long as it didn't move Flat Out). When the Whirlwinds fire at the targeted unit, they can re-roll To Hit and have infinite range. The increased accuracy is nice but the extra range will rarely be useful in a standard game. The main role of the Suppression Force is that it's the cheapest way to add artillery to a Gladius Strike Force at 175 points base.
Finally, we have the Land Raider Spearhead. In my mind, this is GW's answer to Space Marines not having easy access to a super-heavy vehicle. It consists of three Land Raiders of any type in any combination. The Land Raiders gain Armored Behemoths, which means that they ignore Crew Shaken, Crew Stunned, Immobilized, and Weapon Destroyed damage results as long as they are within 6" of another Land Raider in the Formation. This basically makes them light super-heavies, ignoring all damage except Explodes and staying useful until all of their hull points are gone. In addition, they gain Even the Mightiest Shall Fall, re-rolling failed To Wound and armor penetration rolls against gargantuan creatures, super heavy vehicles, and mighty bulwark buildings. Not only do they have super-heavy style durability, but they're good at killing super-heavies.
Basically, if you want a Space Marine super-heavy, your choices are the Spearhead or Forgeworld. The Spearhead seems pretty decent, but it has the downside that only the Standard Land Raider is armed to deal with such hard targets. Hurricane bolters and flamestorm cannons aren't going to threaten super-heavies no matter how many re-rolls they get, so the Spearhead only works if it has three standard Land Raiders. Even then, their lascannons only get a boost against enemy super-heavies. If your opponent didn't bring any, your Land Raiders are a bit more durable but that's it. I would save this Formation for themed games where you know a lot of enemy Lords of War will show up. It's too specialized to bring to standard games.