I thought this project was just about mobile? I'm seeing your new font stack on desktop as well.
Comparing https://web.archive.org/web/20190303224908/https://www.wikipedia.org/ and https://web.archive.org/web/20190304230329/https://www.wikipedia.org/, I'm now seeing Roboto instead of DejaVu Sans. It doesn't look bad, but Roboto is narrower making it a bit harder to read (and the trend towards grey text doesn't help). If I disable Roboto I get Lato, which seems to be a bit smaller yet, and if I disable Lato too I get Arimo which is slightly wider than Roboto but still narrower than DejaVu Sans.