I use it on my 15 pro max. It's a major improvement, but I still don't use siri much. It's gone from murderously infuriating to passably usable. I still use gpt for any sort of exploratory conversations. I haven't bothered trying to use siri for that because to me that's not what siri is for.

Although given how effed up the voice for chatgpt is now with the latest updates I might talk with siri more.

Because I use carplay in tandem with my phone where the map is on the carplay screen and turn by turn directions are on my phone, it's always unlocked so I haven't run into whatever lock screen issue you brought up.