I don't use them, mostly because interactivity is so core to my work. I'm generally distrustful of vendors and people who let you "look but don't touch" at their work - I get suspicious that it would break if they let me really use it. I'd prefer to put up a real working model of a learning interaction so people can see how it works from the inside. From that point, you can always take a bunch of screenshots and animated gifs of the experience to put in a slide deck or video for someone so busy that they will only spend two minutes on it.

I"m interested in an answer to this too. I'm currently investigating these tools, as well as Pastel which looks awesome, Marker.io , and, if you're in a Microsoft shop, MS Test & Feedback.