24h later..
basic animations are smooth, safari worked nice. Ibook is very slow (between 8-12 fps) when scrolling books. When you open a book it's working fine. I notice a huge battery drain compared to iOS 8.4b3. I read a few pages and I went from 100 to 80%. I normally do the same and it uses maximum 2-3%. I will be reverting and will let them fix that.