Disadvantages of using toneAC compared to the standard tone library:
- You must use certain pins (9 & 10 on Uno, 11 & 12 on Mega).
- Uses two pins instead of one.
- Tone duration doesn't run as an interrupt, just a simple delay(). This actually may be an advantage to some for simplicity sake.
But, if you're flexible with your pin choices, this is a great upgrade. It also uses timer 1 instead of timer 2, which may free up a conflict you have with the tone library. It also exclusively uses port registers for the fastest and smallest code possible.
Tim