It is surprisingly fun to play around with the filters and see correlations unfold. If you restrict only a narrow band for number of downloads and leave everything else open, you'll see ratings go up, down, and then up again.
The green line showing the average is very helpful to see the distribution in each dimension. A box plot would provide even more information.
The bezier curves look beautiful on the quantized dimensions: ratings, keywords, price.
diziet's example is released under BSD if you want to adapt it to your data. If you're interested in adding parallel coordinates to an existing application or start from scratch, I'm working on a library here:
nice! We thought about displaying profit from downloads * price but we found that for most of the big apps, they tweak around prices constantly so the profit would vary too much based on when you poll their prices.
Keep in mind though, like makeshifthoop said, price changes (and even more so, in app-purchases) can have another huge effect on total "profiters" -- some top grossing apps are actually free and rely on in-app
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.
Funny tidbit: on firefox especially, forEach and Map functions have a big performance hit compared to doing a native for loop when you're handling a lot of data!