Ok me and my boyfriend personally don't like it. And that's not to say it's a bad movie, but the deeper you look at it the more that they changed how Adrien and Marinette are as people, and things start falling apart from there. I could make an entire post about it to be honest, but Buggachat on Tumblr does a decent enough job of dissecting it.
And that's not even getting me started on how they massacred Plagg, Jesus Christ.
I think the best thing I can say without delving into spoilers is, if you're an S1 fan, you're probably gonna like this. But if you're like me and my partner who adore everything season 4 and 5, yeah this is not it chief. The animation is beautiful though, it's worth it to watch it for that reason alone.
(Also why did they need to make it a musical? It doesn't add anything.)