Let me be clear: Jeff was not saying that we should ever stop believing the gospel. He was saying that as we read the bible, we should be willing to let the scriptures change any of our beliefs and practices. This is, after all, the obvious direct application of sola scriptura. We should be willing to change at any time.
I agree with Jeff. I just don't know if I put this into practice. It is somewhat scary and challenging to commit to changing what we believe any time the bible says to do so. This is challenging because the bible has a way of making frontal assaults on our comfortable traditions. Think for just a minute of a tradition you hold dear. Would you be willing to immediately jettison that tradition if you find that it conflicts with scripture?
Most of us fall into the trap of thinking that we have the Christian life all figured out. We can go on a sort of "Christian autopilot" for days if we are not careful. This can happen if we are not consistently reading scripture. However, if we read the bible regularly, it will have a way of knocking our traditions down to the ground.
On a related topic, we all need to be in church situations where we are encouraged to share our lives with one another. As we do this, we will (or at least should) have the opportunity to lovingly confront others and be confronted by others about areas of our lives that are simply unbiblical.
As for being changed by scripture, we must be willing to alter belief and practice. As evangelicals (especially those who have attended seminary), we tend to elevate belief over practice. We must be careful. The reality is that we actually believe what we practice. Additionally, I think God cares more about some practices than others. For example, God cares more about how I treat the poor than He does what I believe about baptism. They are both important, but I have no doubt that the one matters more than the other.
Will I let scripture change how I think about and treat the poor?
Will I let scripture challenge me at any time on any point?
If we believe the bible is the word of God, then we must do so.