Reduce increment from 0.25
Would you consider reducing the increment value from 0.25 to something smaller, say 0.05? I find that going from 1.00 to 1.25 to 1.50 isn't enough granularity -- I watch talks with my team at work and 1.5 is too fast for all but the slowest speakers and 1.25 is too fast for speakers with unfamiliar accents. I also suggest 0.05 because I listen to podcasts on my phone with a player that supports increments of 0.1, which is much better but still I sometimes find myself twiddling between two settings, wishing there was just one in between.
Granularity would be a great selling point for this extension too -- I have found nothing in the Chrome store that supports anything other than 0.25 and I have probably spent way too much time searching.
Fortunately I have found your extension and it's simple enough that I can tweak it and use my own local version even if you are not amenable to changing it. (I would submit a pull request but the changes are too trivial to warrant bothering.) Thanks!