After we filled up the chat a bit, opening it again takes about six seconds. And sometimes, it starts using 60% CPU doing apparently nothing.
There is a "reply to message" function, but it's useless on images because it only shows the first part of the path to the image (you just see "/home/me/.local/share/jami/8fd7...") and clicking it doesn't bring you to the message in question.
I also tried the Android client, which was usable enough, but it could only receive messages if I had the desktop client too. But that might be because of my NAT.