I haven't really noticed many issues with federation besides the known issues with notifications not always working (not sure if that's federation specific) and the fact that votes don't seem to sync identically. I was comparing a thread here vs its Lemmy host and noticed that while comments transferred in a few seconds, there's something wrong with the vote count. I don't remember the numbers, but it was something like +40 on kbin but +150 on Lemmy, which is a huge difference.