Anecdotally, I barely see anyone using them either, it's maybe 10% of the people 20% of the time. The exception is the occasional coworker with back pain.
There's really no comparison to the sturdiness of a fixed desk. Even tough these were pretty expensive models, they are all very wobbly when used at standing height, which is something I just can't stand (pun intended). So no, even though in the brochure there's a certain appeal to the idea, I still wouldn't want one myself.
But YMMV. Maybe you have the opportunity to try one, to see if it's for you?