There are several tools in FWsim to perfectly synchronize fireworks with music.
Starting with FWsim 2.2, the waveform is visible in the timeline:
To make the waveform bigger, increase the track height under Tools -> Preferences. Note that this will make all tracks higher, not just the waveform.
You can define beats within the music and align your cues to the beats. You can also set markers at the beginning and end of the music, and let FWsim generate beats in-between.
After setting up beats, you can use them. Just drag cues in the timeline and they will snap to the beats of the music. Note that only the launch times snap to the beats, and not the explosion times. This will be improved in future versions of FWsim.
You can disable the snapping by holding the CTRL key.
You can auto-align steppers to music. This adjusts the stepper duration and count so that every shot of the stepper is exactly on one beat.