The headband looks like it ought to be pretty stable and comfortable. I see it also offers a mix of different beam shapes that should be useful for some. I suppose in some uses the Face2Face automatic dimming could be appreciated. And it's regulated, which many of the lower end Petzls are not.
It looks like the battery pack has a screwed together case, so it's likely possible to replace the cells yourself if they wear out.
At 370 grams, it's pretty heavy though, even considering it seems to have a 2-cell battery pack. An Armytek Wizard, which is a relatively heavy headlamp, weighs about 160 grams including one battery.
You should be just fine sticking with Zebralight or Armytek unless there is a specific feature the Duo S has that you really need. If you prefer the separated battery form factor for balance or other reasons, consider the Fenix HP series or perhaps the Nitecore HC70.
I looked up the user manual because I was curious to see if Petzl had anything else to say about what makes it worth $450. The only interesting info I found there is the color temperature is specified as 6000-7000K. Ugh.