If by "amazing" means "I need an explanation to see what I'm seeing", then I agree with you.

Analytics visualizations are great when they're pretty, but if they aren't comprehensible, you've failed. In the vast (>1) user testing I've done with horizon graphs, it just isn't grokkable.

People in general don't want to look stupid, so they aren't going to volunteer a "hey, what the heck am I looking at here?" They'll just assume they aren't smart enough to get it and be quiet.

Agreed; horizon charts take some explanation. However, once you understand what they're showing, they become quite natural. That makes them suitable for dashboards that are monitored by a regular audience (say, production engineers, stock traders), since the viewer learns the first time and then benefits subsequently from the concise representation. However, I probably wouldn't recommend them for a mass audience in a one-off visualization, where the effort to understand might be beyond the viewer's patience for a single viewing.

I think most visualizations require a bit of explanation to understand. The standard rrdtool graphs in Munin, for instance, are surprisingly complicated to understand the first time you see them. And smokeping is a fabulous tool despite having a totally idiosyncratic display. Horizon charts also take a little time to get, but not much.

This appeals to an intuitive sense, but I question the validity of claiming that there exists an information dense format that does not require training to read. Do you have an example of one?

yes, it needs explanation but:

- you do not confuse it with something else when you 1st see it.

- one glance at the image from the link I posted and you instantly knows how it works!