One thing I've never understood about Genesis is how there could be morning and evening if the sun wasn't created until the fourth day. For that matter, how could there be days before the sun was created, since a day is one revolution of the earth around the sun? This is one of the reasons I don't think it could be six literal days.
I'm an idiot. A day isn't a revolution around the sun. Nevermind.
The frame of reference in Ge 1:2 is the Spirit of God hovering over the waters of the earth. The fourth day isn't necessarily the sun being created, it's the sun becoming visible on the surface of the earth after eons of an opaque atmosphere.
This is one of the reasons I don't think it could be six literal days.
The Hebrew word yom, translated as day, has three literal meanings - a 12 hour period, a 24 hour period, and a long indeterminate time. It would be a literal translation to say that the events in Ge 1 took place over six long epochs - notice there is no ending mentioned of the seventh, which we're in...
Actually, RaSh"I (in his comment on the verse in Genesis 2 on "the day G-d created Heaven and earth") says that actually everything was created at once and then individuated on the various days. However, in his comment on Genesis 1:1 he says the first thing created was the waters. But at any rate, the light created on Day One was not the light of the sun but the supernal spiritual light which is reserved for the righteous.
I don't understand why six "days" without a sun (during a period when everything was being created and which is unlike any time after) is a problem. That's like asking where G-d stood when He created the world.