So you want to be a Trooper! (pew pew pew)

Here's a quick overview of the class I am currently playing in SWTOR. I have been leveling Medic Commando, so this is mostly from that viewpoint.
Troopers are a hybrid class. Their storyline involves being part of the Havoc Squad, an elite trooper squad within the Republic. That's all I'm going to say for now. The storyline is the best part.

Power: Troopers use Ammo as their main resource. Ammo is an interesting power source. The more Ammo you have, the higher your regeneration. At full Ammo, your regeneration is about 0.6 per a second. Here's a full look at regen rates.
Betwen 8 and 12 ammo: 0.60 ammo per second
Betwen 3 and 7 ammo: 0.36 ammo per second
Betwen 0 and 2 ammo: 0.24 ammo per second

When you hit 10, you get to choose between two Advance Classes. While both AC's offer DPS specs, your choice affects whether you'll be able to heal or tank.
Vanguard: The Tank AC. I don't know much about this AC. I believe the dps spec in this tree focuses more on closer combat. The Tank spec relies on activating shields to fend off damage.
Commando: The Healing AC. This is also a full on range DPS class spec too. This is Leda's AC. Medic Commando's excel in single target healing, as well as longevity thanks to our unique system of Ammo and regen. We are limited as healers by two things-we do not have an in-combat rez (think Rebirth), and we do not have a powerful AOE. Our largest AOE is a 3 person one. Still. Commando's excel where they are strong. With proper Ammo management, Commando's are competent healers.

Weapons and Armor
A trooper uses Heavy Armor, with primary stats of Aim and Endurance. This does not change when you pick Commando or Vanguard, but the stat priority might change (tanks probably want Endurance more)
Troopers use big guns. Woot! GUNS!!!!
Okay. Vanguards use Blaster Rifles.
Commandos get to use Assault Cannons.

Hammer Shot
This is the ability you need to know. It is free of cost, and allows you to regen your ammo, but continually do damage or heal. It's important to work this into your rotation so you can be giving a constant dps or heal.
As a Commando, at level 14 you will get Combat Support Cell, that changes your Hammer Shot to heal if targeting a player. It's the green beam. :) You use Hammer Shot, and eventually Medical Probe, to charge your weapons. When you hit 30, you use Supercharge Cells, which increase heals and Ammo regen, as well as enhance your healing spells. It's like Tree Form, except a little less powerful but all the same awesome.

Strengths

•  Heavy Armor: allows you to take more hits then normal. Aim is our primary dps/healing stat increasing ranged damage. Endurance is Stamina and Health Regen.
• Strong AOE: I have found that I can easily, at level 25, take out a group of mobs with just two AOE moves. Simple, effective, easy and fast. I can't do that on my Consular. 
• Ammo: I love Ammo. I think it is a really neat power source. The regen mechanic works well, and if your manage it properly, you can never run out of Ammo.
• Companions: We share gear with the first two companions we get, allowing us to easily hand down our gear instead of having to worry about making sure to find or purchase different gear for them. I find this a positive.

Weakness

• Companions: Unless you're a tank, the companion choices in the beginning are kind of meh. As a Commando medic, I would've preferred a Tank right away, but instead got a range dps and a healer. It's not much of a problem, but I wish it was different. If you let your companion run in first to hold onto threat, you risk him being gunned down quickly, while if you end up getting aggro from all the mobs, especially Strong mobs, it feels like
• Lack of AOE Heals: We only have one AOE heal, Kolto Bomb, and it's not nearly that strong, nor does it cover a lot of players. It's also an area spell, so hope everyone is next to each other, or use it on Melee. If Commandos are more tank healers, then I think this won't be a big deal, since Kolto Bomb can be talented to help stave off damage, making it effective for Tank/Melee combos in Operations. But for Flashpoints, it can be a hit or miss. 
• Early Levels: In the beginning it feels like you gain abilities slowly, and you're basically just Explosive Round-ing your way through combat for a while. Hammer Shots, while effective in management,is a weak attack. Of course, once you get AOE dps and the like, you'll start bum rushing your way through mobs. 

Leveling Experience (1-25)
Leveling feels a tad slow because you don't have many attacks in the beginning. While Explosive Round is pretty neat- it knocks down weak mobs in a small radius around the target, it's kind of boring. The only other move you have is Hammer Shot, which is fairly weak.
Once you get your AOE moves-Pulse Cannon, Mortar Volley, and Hail of Bolts (Commando)-leveling becomes a bit easier. While longer fights require you maintain a steady amount of Ammo, you can blow through your Ammo in short fights because you have Recharge and Reload (basically free water and food) to recover quickly afterwards.
For Elite mobs, it's pretty easy to solo them with the right tactics. I mainly send Aric (DPS Companion) in and load the heals onto him. It might take a bit of time, but it's easily doable.

I hope this helps for anyone starting out as a Trooper. I'll probably post some thing about Medic Commandos as I learn how to heal. It's been fun learning something different then the usual. I purposely avoided the HoT healing class (Sawbones Scoundrel Smuggler) so that I could do something different. My next class to post will be the Sith Inquisitor, which is basically a Jedi Consular. But with lightning. Thus cooler. Mwahahahahha.....