some problems faced were economic, cultural, and ideological. Many east lost a lot of money in the conversion of money. Their industrial capability was very low compared to the West and it needed one huge over haul. Some cities got repaired faster than others of course.
Envy and bitterness still exist from West to East just as their is in the USA with North and South. Maybe in a few generations that have grown in a united Germany will the divisions dissapear.