Overall, I'm liking it, but I have some critiques:

1. The apps won't follow hyperlinks to third-party servers. This is not Lemmy's fault; the Universal Links feature of Apple OSes and App Links feature of Android were not made with federation in mind. This will be a tricky problem for them to solve without getting seriously technical.
2. I don't like how external links don't open in new windows/tabs by default, and there appears to be no preference to fix this.
3. There appears to be some bugginess with the web interface and voting where, if I upvote something, the upvote may disappear a second or two later. But if I refresh and re-read the comment, my original upvote stuck.
4. There needs to be more centralization of subs; as of now, there is so much duplication that it's worse than Reddit. Reddit has some forked subs, mainly on ideological grounds or because of mergers, but it's got nothing on Lemmy so far.
5. When reading on the web, my view jumps around a lot. I'm guessing it's loading in new comments as they come in on the server. That's fine, but the abruptness of the whole thing causes me to sometimes lose my place. If it's going to continuously load new comments, I would prefer that they be animated, so at least I can observe the change in motion.
6. While I was typing this, I noticed that the page top reloaded with a different topic. I'm guessing that's a bug.
7. It's good to have rules to prevent conversations from descending into chaos. I just hope that the rules are not interpreted too broadly.