January 4: initial release for Windows 10: 20 downloads - After it went live in the Store, I made a quick post about it as well as a tweet. It's hard to tease out what did what (my guess is that being new in the Store made it show up somewhere), but 20 downloads in a day is pretty good considering it had been live in the Windows Phone Store for a long time and was getting an average of 1 download a day.
January 11: blog post on reddit, retweeted by @msdev: 1-3 downloads - I wrote my post about UWP apps which included a link to Know Your States (and SatRadioGuide) at the top. It was pretty high on reddit's wpdev and windowsdev for a while, and my original tweet got retweeted by @gcaughey (9.6K followers) and @MSTechRewards (22.8K followers). Despite all of that, the app got very few downloads.
January 14: article on WMPowerUser: 64 downloads - I had submitted my article a few days before and was excited to see it get posted; when I had done this for an earlier app, I got a spike in downloads, and the same thing happened this time! Note that the article is word for word what I wrote (which is why it's a "Developer Submission"), so be careful about what you write!
January 20: review on Windows Central: 226 downloads - I had given up on Windows Central since I had tipped them a week earlier, but lo and behold they reviewed my app! I would say the review was mostly positive, and the (on-topic) comments were reasonably positive too. And obviously it blew everything else away in terms of downloads (and in-app purchases too!), which is why Windows Central is still the gold standard of getting your app out there.
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