I have the Callaway Mini driver from a few years back, but to be honest it hasn't been used very much.
I like the concept... I can adjust the loft from 12º all the way up to 16º and it is a very handsome-looking club. But... the oversized head and deeper face make it very challenging to use off of tight lies as a fairway wood option, at least for those of us who struggle obtaining a shallower angle of attack on our fairway wood shots and tend to come in more steeply. I love it off the tee on the shorter par4's, and perhaps as an option on the longer par3's at my club into the wind playing 200 yards or better. But just like every other club - it requires a good swing and there's not a lot of forgiveness off the deck... you have to be exact.
Of course - that's more of a swing-flaw problem than the overall design of the club.
Hoping that perhaps next season I can tidy up that aspect of my long game and put it in the bag a little more often.