Editing text is very frustrating (but it sounds like the 1st iPhone was on-par). The keyboard doesn't always appear or disappear when you'd expect (but you can manually open or close it in Phosh). The biggest frustration here is that the text editing context menu (Copy, Paste etc) doesn't appear at all consistently.
There's also a bug where the context menu appears when it shouldn't (https://gitlab.gnome.org/GNOME/gtk/-/issues/5540), which makes several apps more awkward to use.
Phosh as a shell is mostly fine. The spatial model doesn't really make sense, so it's not as nice to use as the mobile version of Gnome, but that's still pre-alpha for now. Phosh hides the window's close button for some reason, and overrides that setting on every restart, so until apps switch to the new dialogs (which landed yesterday), even closing a dialog is awkward.
Overall it feels very cobbled-together for now. Files and Camera don't work properly yet, so Mobian has replaced them with Portfolio and “Camera (Dev Preview)” (which is actually a completely separate project called Millipixels that looks like a tech demo). Firefox has been heavily modified, including the bizarre decision to put the headerbar at the bottom of the window(?!) unlike any other app, and hide a load of menu options.
And then there's the general fit-and-finish I'd expect from Debian (compared with Fedora). There's a useless “Advanced Network Configuration” app that appears in the app grid, but apparently isn't a real app, because when you try to view its details Software says “Sorry! There are no details for that application”, so you can't get rid of it, whatever it is. Also, Evolution Alarm Notify; but at least I know how to prevent that from starting. (There's less of this sort of thing than with Ubuntu, though — there aren't 3 separate apps for installing software, updating software, and everyone's favourite pastime, configuring software repositories.)
It is possible to use it for basic tasks, and for me personally, I'd rather put up with good-faith bugginess than have to deal with something that assumes I want a Google account.