Fast enough, most of the time.

_delirium · on May 8, 2014

I find it fast enough for reading, but not fast enough for skimming or navigation. If I want to page through a book quickly to find something, it just lags way too much rendering the pages; I have to stop every 5 or 10 pages and wait for it to fill them in, or I'll be paging through nothing but whitespace. But it's fine except for that.

bthorben · on May 8, 2014

Keep in mind that PDF.js is an engine + a viewer. Just a fast engine does not make a nice experience. There are many things in the viewer that one can do to make the experience of using it feel a lot faster.