According to Brant Gardner, there are two opinions about the identity of "the Spirit of the Lord" who introduces the vision to Nephi (1 Nephi 11:11). One opinion is that it is the spirit person of Christ, and the other is that it was the spirit person of the Holy Ghost.
Bruce R. McConkie expresses the first view:
To gain a sound gospel understanding, the truth seeker must determine in each scriptural passage what is meant by such titles as Spirit, Holy Spirit, Spirit of the Lord, Spirit of God, Spirit of Truth. In many instances this is not difficult; in some cases, however, abbreviated scriptural accounts leave so much room for doubt that nothing short of direct revelation can identify precisely what is meant. We know, for instance, that the Spirit personage who appeared to the Brother of Jared was the Spirit Christ, for he so identified himself. (Ether 3) But when we read the account of the appearance of "the Spirit of the Lord" to Nephi (1 Nephi 11), we are left to our own interpretive powers to determine whether the messenger is the Spirit Christ or the Holy Ghost. Presumptively it is the Spirit Christ ministering to Nephi much as he did to the Brother of Jared, for such is in keeping with the principle of advocacy, intercession, and mediation, the principle that all personal appearances of Deity to man since the fall of Adam, excepting appearances of the Father and the Son together, have been appearances of Christ." ("Spirit of the Lord," Mormon Doctrine, p. 752; see also The Mortal Messiah, Vol. 1, pp. 413-414).
The opposite interpretation was espoused by B.H. Roberts and James E. Talmage, among others:
That the Holy Ghost is capable of manifesting himself in the true form and figure of God, after which image man is shaped, is indicated by the wonderful interview between the Spirit and Nephi, in which he revealed himself to the Prophet, questioned him concerning his desires and belief, instructed him in the things of God, speaking face to face with the man. "I spake unto him," says Nephi, "as a man speaketh; for I beheld that he was in the form of a man, yet nevertheless I knew that it was the Spirit of the Lord; and he spake unto me as a man speaketh to another." (B.H. Roberts, The Seventy's Course in Theology, Fifth Year, p. 60; see also Articles of Faith, Chapter 8, pp. 159-160).
[Brant Gardner, "Brant Gardner's Page, "[http://www.highfiber.com/~nahualli/LDStopics/1Nephi/] 1Nephi11.htm, pp. 6-8]