I've had a G15 for quite some time now, and back when I bought it, I largely did so for the sake of having programmable macro keys (or g-keys as logitech calls them). What I have discovered, however, is that I almost never use them. In the vast majority of games I play, I have never been able to find a reason to use these keys. 
 
So I wonder now, if any of you have bought similar keyboards (or mice), only to come to the conclusion that you (almost) ever make use of these programmable keys.

Only for WoW but I don't play anymore so I suppose not.  Still love the keyboard though.

I have G5 and G6 bound to "Gl hf!" and "gg". 
 
:)

I don't have macro keys. I have a bunch of things called function keys that seem to do nothing at all most of the time. Maybe I could bind those...