Truthfully, my knowledge is second hand. I haven't spent a ton of time with it, my coworker is the one who had issues learning it. I've spent a little time with it, and haven't had the same issues he ran into.

I think the issue comes from the learning curve between jQuery and Mithril. Coming to Mithril from React I'd imagine would be relatively easy, where coming to it from JS spaghetti would be rough due to the lack of adoption and step-by-step tutorials that exist compared to React.