It's been bad for me.
All those hate filled posts everyone talks about? I never saw those on Reddit, because I had a couple dozen technical subs (r/emacs, r/PLC, etc.) that I'd browse and rarely if ever strayed from those. Reddit was big enough that the specialized subreddits generated enough content for my use case.
Some of those communities exist here, but they're practically empty. So I wind up doom scrolling on All, which is full of tankie garbage and political propaganda.
I dunno, while I like the idea of Lemmy, I don't think it's likely to ever get the traffic you need for my kind of use. I probably just need to diversify my phone use and visit other sites.