As funny as this can sound, I believe a requirement to tithe does such tremendous damage to the church.  Its all in the picture of God that is created from being under this law.  If we feel condemnation for failing to tithe, it is pretty difficult to want to draw close to God.  And on the other hand, if we do tithe because we are required to, we can easily believe that God now owes us something and self righteousness now becomes our enemy.  But, if we give or even tithe out of love, we will expect nothing in return, for it is given in love.  The person we give to is our focus, in making Him happy.  And when given in love, we are not looking for anything back from Him.  I believe this is when we will receive back from God.  When our giving is not focused on what self will receive.  This gives God an opportunity to give back to us, and He gives everything in love.  It really is important to see the truth about not living under the law.  Jesus fulfilled the law and we are free!