As at the begin of every new quarter since a couple of years, I've updated the Contributor Statistics on our wiki.
Naturally the most noticeable thing is the large jump in new users and active users starting in April 2016, which is naturally mainly due to new incoming edits from maps.me users. This is, on first principles, naturally not a bad thing, and annoyances due to bad edits aside, exposing more people to OSM is good.
What I have however noted in discussion is that the impact of the growth of the raw number of contributors is massively overestimated. For example the number of edits (not changesets) per month is essentially unchanged:
Which is not a surprise given that a maximum 0.18% of the edits per month in 2016 to date have been made with maps.me even though at least 1/4 of the active users used the app in the relevant periods. A preliminary comparison with editors that started off with iD show that over the same period the total number of edits per contributor using maps.me is smaller too.
There may be some longer term gains that we can't see yet, at least anecdotally I've seen one maps.me user do an initial edit and then switch to iD, but the numbers indicate that right now that is the absolute exception.
[Update] Small clarification: the 0.18% number includes all maps.me edits not just new contributors.