I will be the first to admit there are probably other instances of Holy Spirit "baptism" in the New Testament. However, this is not where salvation takes place.
No it's not. In fact, in many cases (e.g. Philip's evangelism, my own personal experience), it took place some time after the person had come to the Lord. My only point is that we have to be careful in limiting God in how He chooses to display His power and Spirit.