I have the Osmo 2 and it's great - the 3 looks even better!!
I had the Osmo 1 and was considering upgrading to the model 2.
Then model 3 was launched for an attractive price.
I don't regret the upgrade.
Compactness offers exactly the same benefit as the difference between a camera you have with you versus one you left at home.
There is hardly an excuse to leave it home, so it gets used more.
The USB C charging port makes it more future proof (and requires fewer cables).
The Phone's connector port is not obstructed when in use, so the camera can be charged while in use, or an external microphone can be connected.
The stabilization is great, and the automatic subject following is quite good, also in front of busy backgrounds. It's a mature product, with many clever options.
Cheers,
Bart