Okay, what can I do with it?

Everything! better_launch can do everything ROS2 launch can and some more. It's also faster, more reliabel, and comes with complete API documentation and many examples.

• create nodes, composers, components, namespaces, etc.
• create subscribers, publishers, services, etc. on the fly
• predictable execution allows you to interact with nodes right after starting them
• include other better_launch launchfiles
• include and be included from regular ROS2 launchfiles
• manage lifecycle stages
• remap topics using simple dicts
• launch arguments passed directly to your function
• easily locate files and load configs
• manage nodes from other launch files
• manage your node using a nice terminal UI reminiscent of rosmon

For a quick comparison, bravely unfold the sections below:

ROS2

# Taken from https://docs.ros.org/en/jazzy/Tutorials/Intermediate/Launch/Using-Substitutions.html
from launch_ros.actions import Node

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument, ExecuteProcess, TimerAction
from launch.conditions import IfCondition
from launch.substitutions import LaunchConfiguration, PythonExpression


def generate_launch_description():
    turtlesim_ns = LaunchConfiguration('turtlesim_ns')
    use_provided_red = LaunchConfiguration('use_provided_red')
    new_background_r = LaunchConfiguration('new_background_r')

    turtlesim_ns_launch_arg = DeclareLaunchArgument(
        'turtlesim_ns',
        default_value='turtlesim1'
    )
    use_provided_red_launch_arg = DeclareLaunchArgument(
        'use_provided_red',
        default_value='False'
    )
    new_background_r_launch_arg = DeclareLaunchArgument(
        'new_background_r',
        default_value='200'
    )

    turtlesim_node = Node(
        package='turtlesim',
        namespace=turtlesim_ns,
        executable='turtlesim_node',
        name='sim'
    )
    spawn_turtle = ExecuteProcess(
        cmd=[[
            'ros2 service call ',
            turtlesim_ns,
            '/spawn ',
            'turtlesim/srv/Spawn ',
            '"{x: 2, y: 2, theta: 0.2}"'
        ]],
        shell=True
    )
    change_background_r = ExecuteProcess(
        cmd=[[
            'ros2 param set ',
            turtlesim_ns,
            '/sim background_r ',
            '120'
        ]],
        shell=True
    )
    change_background_r_conditioned = ExecuteProcess(
        condition=IfCondition(
            PythonExpression([
                new_background_r,
                ' == 200',
                ' and ',
                use_provided_red
            ])
        ),
        cmd=[[
            'ros2 param set ',
            turtlesim_ns,
            '/sim background_r ',
            new_background_r
        ]],
        shell=True
    )

    return LaunchDescription([
        turtlesim_ns_launch_arg,
        use_provided_red_launch_arg,
        new_background_r_launch_arg,
        turtlesim_node,
        spawn_turtle,
        change_background_r,
        TimerAction(
            period=2.0,
            actions=[change_background_r_conditioned],
        )
    ])

better_launch (python)

from better_launch import BetterLaunch, launch_this
from rclpy import Timer

@launch_this
def my_start(
    # Launch arguments in function signature
    turtlesim_ns: str = "turtlesim1", 
    use_provided_red: bool = False, 
    new_background_r: int = 200,
):
    bl = BetterLaunch()

    # Pythonic AF
    with bl.group(turtlesim_ns):
        turtle_node = bl.node(
            package="turtlesim",
            executable="turtlesim_node",
            name="sim",
            # Pass parameters directly 
            params={"background_r": 120}
        )

        # Convenient API for common tasks
        bl.call_service(
            topic=f"/{turtlesim_ns}/spawn",
            service_type="turtlesim/srv/Spawn",
            # No weird types like passing dicts as strings
            request_args={"x": 2.0, "y": 2.0, "theta": 0.2},
        )

        if new_background_r == 200 and use_provided_red:
            turtle_node.is_ros2_connected(timeout=None)
            turtle_node.set_live_params({"background_r": new_background_r})