I'm using one right now; as to if you should get one: The only major benefit for me is that it allows me to put my body into a different position. Sitting too long in one position causes me aches and pains.

I try to keep moving while standing (fidgeting, but on purpose). I'd guess the health benefits are marginal, but the comfort benefits exist.

I have a four-legged motorized standing desk which is expensive, but wobbling drives me absolutely nuts, and I just won't do it. It was a major deal-breaker for a long time.