For me, latency has simply been cut in half - and consistently so.
Previously, there would occasionally be a noticeable delay when turning on a Thread bulb using a Zigbee button or an Aqara H2 wall switch. It didn’t happen often, and it was minor, but it did happen. I’ve had the V4 for a while now, and I still catch myself smiling sometimes because the response time is just so low.
I spent several years working at a well-known music software company, where I became extremely sensitive to latency issues.