Roel,
I believe that the Hebrew term used in Genesis can only be interpreted as a literal day, and there is very little point in expanding that by multiples of 1000; If God can create the universe in 1000 X 6 days, why not make it six?
He is infinitely powerful...so why should we assume that he took such a long time? If you believe that God exists and created the Universe, you might as well take His Word for it.

but I guess we're not supposed to talk about the bible, hey?