I had to use their closed-source, bloated, binary blob GUI clients, couldn't logs the channels I was in (and so relied on having to log in to their servers to get backlogs, which was super annoying), and needed invites to get in to channels.
Apart from the superior multimedia capabilities of these clients, I saw absolutely no advantage of them over IRC clients (which could do useful things like logs all mentioned URLs and mentions of my nick to separate, logged tabs, and which I could run from the terminal and even from within Emacs).
I really hope Matrix is better in this regard, and I'm trying to keep an open mind, but so far attempts to create next generation chat services have been really underwhelming.