On the contribution side, the switchover also had a positive impact on new user activation [1]. 

It’s too early to tell if this change in new user engagement will persist (we probably had a large number of testers among the first signups) and we know that by design (anonymous edit restrictions, prominent CTAs) we should expect to see a higher conversion for editors on the mobile site, but these results are very encouraging: we’re seeing a much higher rate of new users to contribute to start editing Wikipedia in an environment that is more appropriate for tablet devices.

Dario

[1] measured as the proportion of newly registered users who complete at least 1 edit in their first 24 hours, English Wikipedia.
[2] https://trello.com/c/LKVK7RfL/351-tablet-switchover-and-editor-activation