Call quality depends on a lot outside the app - Wi‑Fi, mobile network, the voice provider, your phone, or the other person’s line. When a call started breaking up, you couldn’t tell which one was the cause. And once it ended, there was no easy way to tell us how it had sounded.
Now you can. Signal bars on every call show your connection while you talk. Tap them for details and a tip. After you hang up, a quick star rating tells us how the call sounded.