A few comments on the ideas in this interesting thread:
1. Are Mormons Christians? Just today I read an article in sltrib.com about the Baptist leader Richard Land, who talks about classifying Mormons as a "fourth Abrahamic religion." A religion professor once told me that any sincere and competent person who self-identifies as a Christian should be regarded as a Christian.
2. I am a convert to the LDS church. To me, the historical questions about the Book of Mormon were rather like the historical questions about the Bible. There is no evidence of a worldwide flood, and I don't see how every species of land animal could possibly fit into an ark of the dimensions given in Genesis. I have read that there is surprisingly little archaeological evidence for the Exodus. (Look up "The Exodus" in Wikipedia and see the section about historicity. It mentions anachronisms and contains this very interesting quote: "The consensus among biblical scholars today is that there was never any exodus of the proportions described in the Bible, and that the story is best seen as theology, a story illustrating how the God of Israel acted to save and strengthen his chosen people, and not as history. Nevertheless, the discussion of the historical reality of the exodus has a long history, and continues to attract attention." The rest of my family is Christian but non-LDS. They rib me a lot about the so-called historical problems of the Book of Mormon but they believe in the literal accuracy of the Bible, including the Exodus. Just the other day a Christian was asking me about the DNA data and the Book of Mormon. I hated to break the news to him, but that same DNA data points to Africa as the origin of humans, not to a Garden of Eden between the Tigris and the Euphrates.
3. The U.S. Declaration of Independence presents many, many historical facts (mostly complaints against the deeds of the King of Great Britain). Suppose that someone examined these historical claims and found that not all of them were perfectly accurate, and then argued that the entire Declaration was void and valueless because of a few errors in facts. That would be madness. We all see the Declaration as a set of noble ideas within a historical context, but the ideas have their own freestanding value. The historical context simply makes the ideas easier to understand. I've always felt the same way about the Book of Mormon. I can't prove one way or another whether the historical events in the Book of Mormon ever happened. A lot of people say they did happen, so I'll simply note that and move on. The power of the Book of Mormon flows from its description of how God moves and acts within the human world, not from the historical details of that human world.
4. I have also tended to compare the LDS church to a raindrop. You know how raindrops form? The air holds a lot of moisture, but then something happens to make the air unable to hold the moisture. The moisture then condenses around the nearest handy thing, like a speck of dust. To me, the Book of Mormon is like the speck of dust, and the motions of God are like the moisture. A huge "raindrop" called the LDS church condensed out of thin air around this Book of Mormon, but a lot of people confuse the speck with the raindrop.
Just my thoughts.