Yes, compare with 2.x, the most change is the new structure. There are no more core or commonapp packages, everything is divided into components, and plugin-able. The new structure is more clearer, and reduce the components dependencies.
I like this idea, now it's really easy to implement your application base on ofbiz framework and adopt the exists components against your application scale.
Can not input Chinese with current OS, please bear my chinese-english, :)