Rajagra: What I do is to send two VolUp for each keypress and three VolDown for each keypress. With hotkeys, you don't need/want the same precision as with a slider and efficiency is more welcome (but as you can see I could get any setting by overshooting and backtracking if I wanted to!). Personally, I don't care if the display doesn't exactly match the clicks but it would get annoying if a click seemed to do nothing.
SC040 = Volume_Down 3
SC041 = Volume_Up 2
Ripster: Can you make the AHK popup react to ANY volume changes like the weird-name-app does? Because your example with hotkeys both setting volume and displaying tool tips at the same time is suboptimal for my needs. Therefore, weird-name-app wins - plus, it's oo pretty.
I'm pretty sure it can be done, by using OnMessage - but I don't know which messages to listen for and I can't be arsed to research it.
Tip for tools: I'd use a tray tip instead, to ensure a known location, a nice look and compliance with implementation paradigms (tool tips are for info about whatever you're mousing over, whereas tray tips are for info about resident stuff - like AHK scripts and the volume controls). Remember that tray tips are buggy and so you'll need to send an empty tip after a little while to clear it.