10 Cents Today, page-156

Dropbox modelled 2% conversion of free users to paid. At scale, 1-2% is about par for conversion. So I think your original analysis is right and 5% is too bullish.

Naturally, the NOR designers will spend time and money optimising the experience to maximise conversion and the upsell and increase ARPU. I haven't used the app yet as I am an Android user but will be interested to see it operate first-hand.

If the ARPU increases steadily as engaged user numbers rise then it has a lot of potential. US VCs generally only get excited once downloads get to 20 million, or engaged users to 5 million. I like using that as a rule of thumb for growth and virality and NOR suggests it could get there on current trajectory.