This is a well-written and very clear paper. It covers several aspects that went unmentioned in the Gizmodo article, and highlights that although building such a device may be trivial, evaluating and studying it is not.
Some highlights: the paper covers how the device was built in detail, including information on the three safety mechanisms used to ensure the operator doesn't get exposed to infected blood (shatterproof plastic capillaries, epoxied sample holders made from drinking straws, and sealing of the capillaries inside two paper discs). It is exclusively made from low-cost materials, but it's more than just a piece of paper, handles and some string (fishing wire).
The paper also covers the physical dynamics of the "paperfuge" in great detail, analyzing its rotational dynamics and building a theoretical model of motion that agrees well with the physical observations (captured with a 6000fps high-speed camera). It also shows that the max RPM varies with disc size, with 125000 RPM for a small disc (5mm diameter). The paper even mentions that this was submitted as a Guiness World Record.
Finally it shows that the paperfuge produces sample separation results on par with electromechanical centrifuges using similar spinning time (1.5min for paperfuge, 2min for centrifuge for plasma separation), and does an analysis of the resulting blood samples.