I've only used it one time so far, but happy with result. I'm talking four days ago. I really would like to wait another couple of weeks until I've done it again to actually rave about it.
My one gripe would be, when buying six bottles of serum, supposed to use new head for each bottle, maybe you should do a pack with six heads too, that would make sense to me.
Contact me again in a couple of weeks and I'll update you.