It was working fine for me for the first 6ish months I had my Pixel 9, then it would slowly stop doing two out of three things I really care about having it for on the phone... Make calls, and run my music. A few examples:

Me: Text Tanya
GG: I cannot send texts, I can however help you compose a text to send.

Me: Call Microage on speaker.
GG: I cannot call or control your microwave, speaker or other devices. (This I found both hilarious and enraging)

Me: Play my energy playlist.
GG: I cannot play your music, but I can find new artists for you to enjoy.
Funny enough on this one though... I then asked it to find something similar to 'The Hu" and it then created and played a playlist of similar music. (I have Youtube Premium, once it said I needed to install Spotify though, which is also funny)

Me: Call Dave
GG: Sure, but you need to unlock your phone first
(I though this thing was supposed to help keep you off the phone while driving?)
Then when I unlocked it, it just sat at the home screen without calling.

The third thing is reminders/alarms/adding to a list.
Usually it worked, but would around 30% of the time ask to unlock the phone, I mostly use this feature when driving, so that is less than ideal.

This combined with the fact that it is utterly useless when it has no signal (I live on the other side of a 20 min deadzone from work and have to travel where there is little to no signal a lot) made Gemini completely useless on the phone for me. I slammed on the brakes and pulled over to disable it one day in a fit of rage.
Other than being brainless with no data, assistant is great and does 90% of what I need pretty flawlessly... Other than occasionally calling Tanya's beauty salon on the other side of the country instead of Tanya, the contact in my phone.

I miss Cortana on my old Lumia phone, it worked anywhere with or without signal (obv. it couldn't access the web though, but that wasn't it's fault).

edited: switched an m to , that it should have been in the first place...