Among the highlights of their second quarter financial results, Amazon has stated that sales of the Fire TV have surpassed initial forecasts.
“Fire TV sales have significantly exceeded our sales forecast and we are working hard to increase our manufacturing output. Fire TV app selection has more than doubled since launch due to strong engagement from developers.” -Amazon PR
Amazon is notorious for never giving exact sales figures, so your guess is a good as ours for the true popularity of the Fire TV. The press release also mentions the doubling of the Fire TV app selection which launched with around 200 apps and currently stands at 455 apps.
SourceAmazon Press Release