Upgrading vBulletin 3.8 to 4.0

I looking forward to upgrade vBulletin 3.8 to vBulletin 4.0. What i need to know开发者_如何学编程 is how much effort it will be to migrate. I have about 15 products installed.

Any idea is there any change in hooks or functions or way to call things that i will need to change in products and templates? Also is there any thing that deprecated in 4.0 that i will have to look into?

I found Styles are not at all compatible and Products are not compatible 99% of times. SO i will have to redo styles and also fix custom products and upgrade downloaded products.