I'd be excited to even start using Matrix for instant messaging. Elements seems pretty half-baked on my phone and I'd feel bad for convincing anyone to switch from Whatsapp to it.
We're constantly iterating on Element's UI, and the concepts are getting constantly de-weirded. For instance, one of the things many people complain about is that it's possible (and indeed easy) to end up with multiple DMs with the same person. So we're in the process of defaulting to "canonical DMs" (i.e. one DM for each pair of people). Others complain about the hassle of managing E2EE (verifying new logins; backing up your keys with recovery passphrases/keys, etc) - the Matrix equivalent of the Signal recovery PIN drama. We're going to be reworking that all (again) next year, too. So yeah, the UI isn't perfect, but hopefully we're working on it, and it should get better.
Meanwhile, the nice thing about Matrix is you can use whatever app you like - e.g. SchildiChat is a fork of Element Android, FluffyChat's good too, so use whatever floats your boat.
A big problem for me on any client is the scrollback. It sometimes gets stuck or takes longer than 15s to load the next portion. The only time I've been able to catch up with old pings was if I had the client open in the background.
