How important is the OT for NT Believers?

Joshua Williams, one of my OT profs, has posted a good excerpt from an interview he did about the relevance of the Old Testament. He begins by stating that,

It is virtually impossible to overstate the importance of the Old Testament for New Testament believers. First, it constitutes about seventy-five percent of the Bible. Much of what we know about God, man, and the world is found in the Old Testament. It is important to remember that the Old Testament was the Bible of Jesus and the early church.

It is fair to say that the theology of Jesus and the apostles is an Old Testament theology. We would do well to follow their lead in taking seriously the Old Testament when constructing theology ourselves. 

He sums up the issue by insisting that,

The Old Testament has a rightful place alongside the New Testament as the revelation of God to man. Without its abiding witness, too much would be lost, confused, or placed out of balance.

The New Testament should not overshadow its significance, but enhance it as a testimony to God and His work among His people.