Gunslingers are the DPS only advanced class of Smugglers. All three trees they get are about laying on the hurt. Their prime weapon are dual blaster pistols. (Oddly the other class in the game that does this is the bounty hunter, the horde...er...sith equivalent of the trooper)
There are two unique trees plus the dirty fighting tree that both classes get. Sharpshooter is all about blasters and saboteur is all about explosives. They're both DPS trees and sharpshooter seems better single target while saboteur has a bit more AoE. Dirty fighting seems to prefer bleeds a bit more. I've played mostly the sharpshooter tree.
You've got an energy bar that remains at 100 throughout the game. (Boosted to 110 with certain talents and possibly more with set gear). It initially looks like a mirror of the rogue resource but one twist sets it apart. Energy regen rate is based on how much energy you have. As you dip below certain thresholds your energy regen slows down. This means gunslinger gameplay is focused on trying to keep your energy in the highest tier of regen to maximize long term DPS. Dipping into the lower levels for burn phases and then using their instant regen skill to bring them back up. (They get a cooldown to quickly regen 50 energy) This means gunslingers will have more in common with arcane mages than they do rogues. An energy neutral rotation and a burn phase rotation.
For sharpshooters you'll do most your main moves from cover. When you enter cover your action bar changes, much like how rogues do when they enter stealth. There doesn't need to be physical cover nearby, if not they simply plop down a shield and get all the same benefits of cover. ...in fact it's almost preferable since the cover nodes are annoying in that you're locked to them and inhibit movement since running away and hitting cover will return you to the same node. There's also currently bugs where aimed shot is unusable in natural cover. I'm really hoping we'll get a toggle to ignore natural cover since while it's cool to roll into cover, it's almost ALWAYS worse off than just plopping down where you press the button.
To make things more odd you get a talent that makes charged burts, a main DPS move, instant right after entering cover. This encourages you to shimmy to break cover and then re-enter to get an instant cast burst if needed. (This also refreshes a damage redux ability granted when entering cover) It feels a bit weird to pop in and out of cover and I imagine this is a mechanic they'll tweak. I could see them lumping the instant effect on one of our CDs.
Later level sharpshooter rotations seem based around proc'd effects and cooldowns. Some of your main moves trigger trick shot, which is a follow up shot that's high on damage and low on energy cost. (Important for staying in the regen sweet spot.) In addition aimed shot and charged burst share some buffs they proc as well. Charged shot can proc a quicker aimed shot, and aimed shot procs a haste buff that is boosted by followup charged bursts. I'm not quite sure where speed shot will factor into the rotation but I imagine when the haste is at max from the buff it becomes a more potent ability.
AoE for sharpshooters is limited to just thermal grenades and sweeping fire. Sweeping fire is your basically blizzard style channeled move, except it only hits 3 targets. To make matters worst many tanking classes seem to get an AoE knockback. This makes abilities like this extremely frustrating to use well. On top of that since many of the enemies in the game are ranged and there's even ranged tanks, grouping up mobs doesn't even always happen or seem necessary.
Stat weights are tricky to guess at the moment. Power seems to be a runaway awesome stat since it increases damage much more potently than any other stat. Accuracy likely is your basic cap stat and I feel like at that point crit and surge at the next best. Alacrity (haste) seems a bit weak since it'll never increase the GCD so it seems to be of limited value since only a few of the gunslinger moves have a cast longer than the GCD.
From the other theorycrafting I've read at sithwarrior.com it seems like the general state of balance for the classes is in an extremely rough state at the moment so I'm expecting when they drop their first big content patch there's gonna be an awful lot of changes. It's a lot like WoW classic where certain specs/classes are almost unable to raid at the moment, and others are grossly overpowered. I'm hoping Bioware has been paying attention to WoW and is able to give as much attention to balance going forward as they have their storytelling.