The first occurence of the nPerf speed test in the Wayback Machine is December 2014.
nPerf is a miscellaneous speed test. This is because with a speed of 50 Mbps, nPerf should be categorised as a mainstream speed test, while with a speed of 75 Mbps, nPerf seems to be an ambiguous speed test. Hence it is categorised as miscellaneous.
The nPerf speed test is relative slow. It takes at least a minute to complete the test.
Results below the fold
The interface of nPerf requires a high screen to see the results. With a screen of 1080 pixels high, the results are below the fold. To see the results, you have to go to full screen mode or you have to scroll down.
The results aren't visible in a normal browser view in a normal browser view.
With the browser in full screen mode the results are visible.
All in all, nPerf isn't a bad speed test. However, there are better (especially faster) alternatives available.
In the speed test overview you find all findings regarding the nPerf speed test.