I'm a mod of a small subreddit and during the last 3 months around 10-15% of our visitors used the redesign, 20% browse on mobile, 30% use an App, and the rest use the old design. Engagement is highest in the Apps.
Thanks for sharing this. I use Reddit primarily on an iPhone using the app. I find it enjoyable. Kudos! I like the new React web site as well visually but agree with the usability issues noted here. I have to manually clear all my cookies to be able to login.