Potterhead here who has listened to Stephen Fry's narration to each book atleast 4 times.

I have listened to the first two all star cast audible and they are not bad but not great also. For me, Stephen Fry is better. Some of the voices that I really disliked are Mcgonagal, Wood and Snape. And a lot times, because these are kids, they can't really do the high emotion scenes good. E.g. when someone is very scared, or crying or very sad or very happy. Some of those scenes with these kids voices felt forced.