I tried Hipp Milk once, and would never go back to it. I found that it was a nightmare to make up. No matter how I did it, the powder clumped and I ended up with what looked like cottage cheese sticking to the central vent of my Dr Brown's bottles. It was really greasy too, I had to scrub at the bottles to clean them, and it was just horrendous.
Saying that, I know they have recently re-branded all their formula (new boxes etc) so I have no idea if they changed the recipe at the same time.
I also didn't like that it came in little bags, rather than boxes. Whilst I appreciate that less packaging is good for the environment, I found it an utter faff trying to get the powder out.