This deck is a great entry point into the game. It's incredibly aggressive, highly synergistic, and relatively cheap to build with the only 4 cards (12 for playsets) that will hurt your wallet. Currently Sabin Command is the aggro deck of choice in the meta, but Leia has a huge leg up over that build in the form of action economy.
If you are coming from Magic this concept of action economy is something unique to SWU as there isn't instant speed interaction. Each player takes an action, goes back and forth throughout the turn and the first player to finish their plans for that turn then takes initiative in order to be first on the following turn. Leia's ability to attack with two rebels in one action not only prevents your opponent from interacting with a unit before damage is dealt in a turn, but also helps ensure you get initiative almost every time. All units in this deck have the rebel type. The big swing in the deck is playing Rebel Assault on Leia allowing you to attack with three units in one action!
So their is the rebel synergy but there is a secondary synergy that limited deck building choices, which was For A Cause I Believe In and running 100% heroic aspect cards. This card will hit for 4 damage every time, while setting up your next draw. Incredible value and reach to finish out games.
U-Wing Reinforcement is your late game refill, and can even hit Fleet Lieutenant allowing you to attack in the same action.
Playing against this deck was incredibly frustrating as even when I had interaction I barely ever had initiative to prevent the unit from doing damage in the turn, and if I used my interaction on a unit that hadn't attacked yet to try and stop the bleeding I wasn't going to target the biggest threat on the board. There was even a turn when I was forced to take initiative way before I had used all my resources and units just to try and get on top of the next turn.
I haven't dealt with sideboarding yet, but I would probably look to having some space units to shift into, Karabast for interaction, as well as Guerilla Attack Pod for late game reach.