I wrote this app because i hate to:
1. Sacrifice three of my F-n keys just for volume adjustment.
2. Put my left hand on the keyboard just to adjust the volume.
3. Locate the volume keys on the keyboard by looking at it. (Even if i can type very well, my MacBook Pro keyboard is simply too crowded.)
The iVol app makes adjusting volume so effortless: just press the mouse wheel/ball and scroll it up/down to turn up/down the volume.
Once you do that, an indicator will show up under the mouse cursor. Then you can let go the wheel/ball, and just scroll the wheel/ball without pressing. Moving the cursor out of the indicator to hide it.
I use it everyday and I believe you will find it useful, too!