I think there are many different opinions on this topic.

I think in a sense, they are. For example, in the Doctrine and Covenants, section 68 it says:

"And whatsoever they shall speak when moved upon by the Holy Ghost shall be scripture, shall be the will of the Lord, shall be the mind of the Lord, shall be the word of the Lord, shall be the voice of the Lord, and the power of God, unto salvation"

So basically anything said under the influence of the Holy Ghost is scripture.

However, I do not believe that means that all conference addresses are the Word of God, like the canonized scriptures. In fact, I believe that if one searched, one could easily find conference addresses which contradict each other in some details. Also, I believe that most conference speakers would not put their talks in the same category as revealed canon!

I do believe that some conference addresses are in fact revelations, and I sustain the President of the church as a prophet with the ability to tell us the will of the Lord. However, the mere fact of being a conference talk does not promote "good advice" (how I view most conference talks) into the category of revelation. I believe that from the wording in the talk itself, it is usually clear as to whether the speaker claims revelatory stature or not.

For example, a quick search of the Discourses of Brigham Young finds this passage (presumably given at a church conference):

"In the name of the Lord Jesus Christ, I command the Elders of Israel--those who have been in the habit of getting drunk--to cease drinking strong drink from this time henceforth."

I think that is pretty clear that Brother Brigham was speaking as the Lord's representative, and not just giving good advice. Granted, this particular passage only refers to the alcohol part of the Word of Wisdom, and not the other parts, but you get the idea.

Similarly, a reading of Pres. Kimball's Official Declaration #2

"[B]y revelation [the Lord] has confirmed that the long-promised day has come when every faithful, worthy man in the Church may receive the holy priesthood..." seems to make it clear that it is a revelation.

There have probably been other recent conference addresses which I would put in this category-- for example, Pres. Benson's counsel to read the Book of Mormon comes to mind, as well as Pres. Hunter's counsel to make the temple the "symbol of your membership".