After running Sound of Text, for free on the side for almost 3 years, it received over 100,000 unique users in February 2017, according to Google Analytics.
I think what is most interesting about this growth is that I spent very little effort on it. I only ever "launched" Sound of Text a single time, to Hacker News in 2014. All the growth after that was completely organic.
I think growth is pretty easy when your product is free 😁 Either way, it is fun to see Sound of Text grow.