Pros
- Open Source Game Engine
- It's amazing that anyone may contribute code without restrictions, licensing costs etc.
- Multi threading support is great especially compared all others before Unity 3d(i'm talking about years ago)
- Easy To Learn For those who know nothing already
- Very beginner friendly engine + tutorials available online free = win+win situation here :)
- Good community around forum boards too.
- Great documentation provided within software itself :)
Cons
- Some