It's about the same quality as a budget Android 2-4 phone.
The basics are pretty much down. Kernel support is solid. It can make calls, send texts (MMS mileage may vary), and use data pretty reliably. Web browsing is actually pretty fast with Angelfish. You technically have access to the full repository of Linux ARM software, and some of it even resizes properly to the phone. The camera is usable but terrible. Anbox works for Android apps but is painfully slow and can't share data with the rest of the phone to my knowledge.
Battery life is terrible, I don't think that the phone has power states of any kind, so it's either with the screen on, on with the screen off, or off altogether. Updates frequently break my install, although updating through SSH has been working for me recently on Tumbleweed without breaking anything. Little things like Plasma not having a way to exit the keyboard, apps taking up full screen with no way to exit them, etc.
Performance is painfully slow, but has also improved (for KDE anyways) by leaps and bounds. It used to be completely unusable but now it's merely very slow.
I would say it's somewhere between for developers, and usable, at this point. You could use it with some sacrifices, and still have a functional wireless communication device. It absolutely is nowhere near replacing my OnePlus running Android, however.