I personally believe in baptizing adults old enough to understand what they are doing. I think of Acts 2:38 (saying to first repent and then to be baptized).
36 "Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ."
37 When the people heard this, they were cut to the heart and said to Peter and the other apostles, "Brothers, what shall we do?"
38 Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit. 39The promise is for you and your children and for all who are far off--for all whom the Lord our God will call."
As far as the significance of baptism itself (infant of adult), I think that Romans 6 and 1st Peter 3:21 both emphasize it's importance.
18 For Christ died for sins once for all, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive by the Spirit, 19 through whom also he went and preached to the spirits in prison 20 who disobeyed long ago when God waited patiently in the days of Noah while the ark was being built. In it only a few people, eight in all, were saved through water, 21 and this water symbolizes baptism that now saves you also--not the removal of dirt from the body but the pledge of a good conscience toward God. It saves you by the resurrection of Jesus Christ, 22 who has gone into heaven and is at God's right hand--with angels, authorities and powers in submission to him.
HOWEVER, I find it hard to imagine friends I know who love the Lord, (but who instead practice confirmation as a way of recognizing their infant baptism), as burning in hell because they have a different understanding of the Bible than I do.
When I think of individuals such as Mother Teresa, who lived a life totally devoted to Christ, I cannot imagine her d*m*d for all eternity because she practiced baptism differently than I understand it to be taught.
I am not so self-centered as to believe that I have a complete understanding of the Bible. We, as a church (in the ecumenical sense of the word), can gain so much more by learning and sharing with each other than we can from arguing among ourselves.