After a day of use, I'm incredibly disappointed.
The fragmentation problems, and lack of cohesive community discovery (or even apparently any agreed standards for sharing communities etc. across instances in a way the most popular app can reliably recognise as being a community and not an external link or mailto address) will make Lemmy an absolute non-starter for 99% of potential users.
I'm sure there are solutions, but as it stands I can't see Lemmy gaining any widespread adoption without a significant leap in user friendliness in regard to how federated instances are implemented and managed.
I keep seeing this as well. Probably the most frequent ad I've seen.