Sorry for coming down harsh but I don't understand how to interpret any of the individual curves, since it looks like they are five points on five different axis with a curve fit through them. What's the significance?
Each curve/line is an individual app with each point representing that app's stats in downloads, reviews, etc. You can use the different axis to see trends. Ie, there is (obviously) a correlation between number of downloads and reviews. You can check out a bit about the history of the visualization at http://en.wikipedia.org/wiki/Parallel_coordinates
Parallel coordinates is based on projective geometry, and has a point-line duality with orthogonal (cartesian) coordinates. Points in orthogonal coordinates become lines in parallel coordinates.
Few parallel coordinates applications take advantage of the fact that you can show lines in orthogonal coordinates as points in parallel coordinates though. It's one of the few effective ways of representing hyperplanes and hyperlines. Interpreting that is tricky though. Even people who "get" traditional parallel coordinates would have a tough time at first.
Think of it as a multidimensional scatterplot, where lines are a necessary concession to map N-space to 2-space.
I don't see you as coming down harsh at all, it's a data visualization that requires some math skills. Having an interest in, or understanding of higher dimensional geometry is not for everyone. Basically you can spot positive and negative correlations using these kinds of visualizations.