I've been trying it out for the last week. I have my own opinions, but I'd like to hear others and see if we have common ideas on what is good/bad/indifferent about the Lemmy ecosystem.
It will take years for Lemmy to take off in much the same way as Reddit had slowly built up.
As I and other mentioned before, the main downside of Lemmy is that the community you care about isn't here (and frankly, I don't know if they will even come here at all). Like, we don't have AskHistorians here, and the Lemmy for your hometown or country is either quiet or just completely died. So, I end up having no choice but to return to Reddit to keep in touch with those communities. However, as someone who is privacy conscious since Reddit now sells your data to train AI, I try to log in to Reddit with Tor. But even with the Onion site of Reddit, it won't let me log in at most times because of technical discrepancy with stupid captchas or something. Sometimes I could log in via Tor but most times I'm not able to.
Anyhow, I would love Lemmy to take off as soon as possible but there is teething problem common in new communities. But the pessimistic side of me thinks it may not since so many people have become too invested in Reddit. And the latter intentionally hooked people in for the worst reasons.