My free app is seeing about 500 downloads/day. When it was featured in the "New & Noteworthy" it was about 1500/day. However my IAP conversion is holding at about 2% which, to me, is quite bad.

Another thing to point out is that the author has about 4k Twitter followers, so he does have an existing network of people to expose this app to. It's not much, but its a (free) start.