Well, using it before v1.0 and I can't say the same unfortunately. No changes when it comes to API or very little right.
But "runtime behavior", oh boy. I have gone through unexpected behavior changes in touch event propagation, look and feel, interoperability with old toolkit, performance everything. And when I say compose I mean material3 and all the libraries surrounding it. Perhaps compose itself is not so bad.
But yeah, every time I upgrade, I do full regression manually checking the full App due to the experience in the past