Depends on what you mean when you say nice. Being nice is not necessarily a good thing. Often when a situation comes up where one can either be "nice" or be honest they will choose the "nice" path. This would be the weaker choice in many cases where it would have been more loving, and stronger to take the honesty route.
The word nice used to mean foolish, or stupid. Now we often describe people who are pleasant, polite, and sometimes foolishly kind as "nice". Think about the people you would describe as nice, and whether or not you would list superficial reasons, or deep reasons why you would describe them that way. Often when I ask this question people list superficial reasons. They smile, they are agreeable, they are polite, they are just being nice.
It is really easy to be nice. It is a lot harder to be loving and kind. Nice can fade away like somebody taking off a mask, being nice can often just be a charade( I am picturing a cat going from sweet to hiss when you offend them). When somebody is genuinely loving and kind it will remain evident no matter how other people behave.
Example: A woman is having relationship issues. She is in an abusive relationship but is seeking validation from her friends that she is making the right choice in remaining with her abusive partner. One friend takes the nice approach, "You should do what you need to do, what your heart feels is right,if he makes you happy then you are doing the right thing." the other takes the honest approach, "I will not support you being in a relationship that is hurting you and your children. I really think you should consider whether or not this is the right path." Nice was weak, and honest was strong and loving.
Not the best example but I am falling asleep at my keyboard :p I think I made my point. :)