I often need to visualize data and unfortunately, plotting and working with many millions of points is a key capability. For example, we might have an expensive piece of hardware that we are using and need to understand if an issue we are seeing is a problem in our user software, a firmware we wrote to interface with it, or comes from the hardware itself.

Having technical representatives from each team (each sure that his team has nothing to do with it; can they please go back to their offices now) in a room looking at the same instrumentation data with ability to quickly dig into various features and subsets is a huge help for such problem isolation. At least in my experience it depends on fast interactive plotting and filtering of large datasets.