I really like this add-on, as I can just use messenger and not be disturbed by the rest of facebook. Unfortunately, it just makes the whole messenger part run so incredibly slow that I've ended up giving up using this tool altogether. I hope to be able to come back later and it might run better. The problems are there even though both firefox and SimpleUI are updated to the latest versions. Then it can take several minutes to load messenger. But if I turn it off, we're talking seconds.