The Ending
I really liked the whole anime. It was one of the best for me. But still there was one thing.
After 25th episode it become a bit less interesting and in the end he just made such silly mistake which didn't suit him . I agree he become a bit over confident but still it wasn't like him.
He could have write death of everybody there in the warehouse excluding him. Or use Misa again or have Mikami check the notebook while coming.
That ending was just to show that Light is evil and Good always win against Bad. Even in that case they should have make it better.