The idea for Pop Rock just kind of popped into my head after about a day or two of latent thinking and once I started, I couldn't stop (as my wife can attest). The pressure was fun! Also, I mentioned it in the project notes, but again I just want to give a shout out to fellow Mac indie Mike Zornek of Clickable Bliss for his MegaManEffect, which I adore and which gave me the idea for an app launcher style of project.
I originally had the idea to use iusethis to fetch app popularity ratings, but this proved to be too slow to be useful at app launch time, so I fell back to a basic count of the number of other applications running, which was much quicker.
Since the app was built on Quartz Composer and not on Core Animation, it runs on Tiger too. I've compiled a version for both Tiger and Leopard (though I haven't had a chance to Test it on Tiger yet).