Cons: few more things to consider
1- total raise in temperature, LEDs dissipates high amount of heat compared to other devices. This could affect some sensitive devices specially when the board has to be isolated from surroundings, like boards in ROVs or so.
2- more current means more trace width, larger power supply, higher rated components, much bigger board size thus more overall cost.
3- one more important thing to consider, the expected operating time to devices operated by battery will significantly drop down. Some applications requires devices with long battery operating time. Hot kiln alignment as an example which is the major I'm specialized in requires devices that can operate for long periods of time, 3 hours for example and yes 3 hours is too much long enough because temperature in shells in such cases rises to some how near 350 °C. That means you have to depend on devices that can withstand these temperatures and withstand the circumstances until your job has been done.
1- Nicely looking boards.
2- Attracts attention.
3- Ease of monitoring and troubleshooting.
Conclusion Avoid placing LEDs on boards that are not mandatory. If it has no use then its not worth having to be placed.