A friend of mine (Dave Peters) just posted some great comments (from Dr. Philip Ryken) about why we should read, preach and teach the OT (31 Reasons). My own thought is that in our contemporary church setting, it would appear too often one of two extremes concerning the OT predominate: either improper understanding and over-emphasis (leading to forms of legalism) or improper understanding and no emphasis (leading to an emasculated Biblical worldview). Understanding of the OT should be paramount for every Christian (it was the original Scriptures of the Early Church after all) as it is foundational to understanding the NT. We cannot shy away from the difficult and ugly found in the OT, because it declares the LORD as truly Lord of all and points ahead to ultimate redemption in Christ Jesus.
Preach it Dave :-) !