Do you have the MagSafe case? Because I have the MagSafe case and it has extra magnets on the case. no idea how strong the bond is, but I saw a video of a guy with the apple MagSafe charger and it held pretty good.
Yes, I have the MagSafe case and it has a very weak bond to my Scosche Magic Mount Qi (not enough to hold it up). HaloLock or any MagSafe car mount would have to have considerably stronger magnets for it to work in a moving car.
Being able to stick to a MagSafe charger is one thing but holding the weight of the phone up on a mount requires a lot more magnetic strength.
I want to be more optimistic, as an effective car mount is mission critical, but given the relatively early release of HaloLock, I'm assuming there wasn't much opportunity for testing. We could always get lucky, though...