I've only been on free heels for a season, so take this with a grain of salt...
I currently have a set of garmont syner-g boots, and was looking for something a bit taller/stiffer. I'd been eyeing the ener-g or BD push when I had the opportunity to demo a set of the voodoo's for a few runs. I was on a set of Atomic Kailas (88 waist) with voile switchbacks in fairly firm conditions.
First impression. Very different last/shape than the syner-g. I have an admittedly wide flat foot, and scarpa boots generally don't work for me. Knowing that the liners hadn't been baked on the voodoo, I'm still pretty sure that the arch area and the outside perimeter/ball of my foot would never quite fit right in these boots. My dogs were cramping pretty quickly.
How did they ride?
As expected, they had a significantly stiffer/taller feel than the syner-g's, and had more forward lean. The lean would likely be good for more aggressive folks. Unfortunately, I'm not too aggressive yet (single blacks and blues), its early season, and I hadn't warmed up, so my quads burnt up pretty quick.
The bellows flexed very smooth... significantly softer than the bellows on my syner-g's, which took some getting used to. Once gotten used to, this might help you keep the ball of your foot down rather than tip-toeing, but might be too soft for some?
I had a thin cycling sock on, which allowed me to feel the bellows coming down on top of my foot a little, but not painfully so. A thicker sock would probably eliminate the top of foot feel.
Unfortunately, my feet were screaming in these so I only got 3 or 4 runs, which was only long enough for these quick impressions.
With a bit of liner/shell work, these would probably be a good set for me and I might be able to get used to the softer bellows. However, given that the last of the syner-g/ener-g are pretty similar and only needed minor work, I'll probably go back to those to make life easier.