I finally found a really good review for a panoramic head which explains how to use these things and what's the idea behind it.

link

it look's indeed much better and cheaper than the bogen variation, but I just don't get point how to level this thing in the first place. I mean it's nice to have a level build in, but how do you actually level it?

Specially the whole thing is so simple constructed, nothing can break and the indentation rings are such a nice and simple idea.