Yesterday Google posted a blog post strongly encouraging webmasters to implement the "auto complete" markup on their forms to improve form conversions, especially on mobile devices.
To be honest, I love using autocomplete on my own browser. As a user, it makes my life easier and I am so much more likely to fill out a form, especially on a mobile device, if most of the work is done for me.
The article questioned whether Google would use autocomplete markup in future iterations of its ranking algorithm, perhaps even with the new pending mobile friendly update? Google of course, wasn't clear on the subject one way or another. However, I think this markup is something webmasters should definitely take into consideration, since it greatly improves the user experience.