I prefer to take a literal standpoint in most cases where biblical interpretations are disputed. Some say that the 6 days are symbolic of six ages, but I really dont think so. The Genesis account is accepted to have been written by Moses - though we dont know for certain. Clearly Moses did not witness the events themselves, so they must have been revealed to him in one way or another. As far as the time-line is concerned, for him to embellish by substituting literal days for actual eras is unrealistic IMO.
The Latter-day Saints actually have a more literal understanding of most biblical events than many Christians do, so I can appreciate your perspective. On the other hand, the author of Genesis (regardless of who it may have been) was not a man of science, but a man of faith. God spoke to him in a way that he would have been able to understand and in a language that he would be able to communicate with other people of his time. Here's how I heard it explained once:
"I don't understand why it is so difficult for some people to believe that God is the greatest scientist in the universe, but that he could not explain some of his high tech processes to people who thought a fig leaf was high tech. Even if He had been able to show [his ancient prophets] the whole truth, how could [they] write that down in terms that the rest of the world would understand without a few thousand years of education?
How do you explain to your children how a gasoline engine works or where rain comes from? Is it possible that you answer this never-ending flow of curiousity with 'not quite accurate answers' whichare in terms your children will understand. When God [said] that [Adam] was created from the dust in one day, is it not possible that this answer was his 'not totally accurate explanation' in terms that [people] could understand? How would you explain genetics and millenniums to a man whose first and greatest creation was disposable underwear harvested from the same tree his food was harvested from"?