Yes, I've been using it on and off since it was called Netscape, but the ad blocking leaves much to be desired on iOS.
It's because Chrome and Chromium browsers have like 90% marketshare around the world, so websites are generally catered to function the best with those types of browsers. Having said that, "secure" and "private" are two entirely different things. Firefox is far more "private" than Chrome or Edge, but not as private as Brave out of the box, though Firefox can be tweaked a lot to be very private.
If Firefox allowed uBlock Origin on iOS like the Android version, it would be so much better. But as of right now, Brave has the ad blocking built in out of all browsers that aren't Safari on iOS. But even the iOS version of Brave is gimped compared to the Android version.