First of all, I love the library. It will be my first choice in most applications.
I hope to test the Uno/Mega/Leonardo/ATmega8 with version 1.2, after that it should be ready.
That single line of code makes some of my tests sound a lot better.
I have made a checklist for version 1.2, perhaps there are one to two things that make sense.
(1) The code increased a little (just a little) which is always a problem for the ATmega8
library + example version with 1.0, Arduino Uno : 1516
library + example version with 1.1, Arduino Uno : 1670
library + example version with 1.0, ATmega8 : 1336
library + example version with 1.1, ATmega8 : 1472
(2) The ISR uses millis(), so a roll-over of the millis is possible. The length is no longer fail-safe, so using the delay() function with noToneAC() is preferrable for critical situations.
(3) You don't use the 'L' for long values. I don't mind about it in the sketch, but you could use it in your library. I prefer to use 0L, 256L, - 1L and so on, when long integers are involved.
(4) The examples have the extension *.pde. I would prefer *.ino
(5) In the example you use '/* .... */' for comment, but everwhere else '//'.
(6) In the example, you use a potmeter. But for a small test with the library, a very quick result (showcase) would be needed. And a potmeter will make it unnecessary complicated.
(7) You made 10 volume steps, which is great. But for a 'ping' sound, a smooth decrease of the volume is needed. Or am I asking too much for the library ? Are there open source examples of tunes with volume ?
( 8 ) Why is the sound different for this example ?
int i, freq, vol;
for (i = 0; i<5; i++)
{Â
 freq = 900;
 for (vol=10; vol>0; vol--)
  toneAC( freq , vol, 60, false);
 freq = 540;
 for (vol=10; vol>0; vol--)
  toneAC( freq, vol, 60, false);
 delay( 3000);
}
for (i = 0; i<5; i++)
{Â
 freq = 900;
 for (vol=10; vol>0; vol--)
 {
  toneAC( freq , vol, 0, true);
  delay(60);
 }
 freq = 540;
 for (vol=10; vol>0; vol--)
 {
  toneAC( freq, vol, 0, true);
  delay(60);
 }
 noToneAC();
 delay( 3000);
}