24th April 2009 10:35
I had a similar thing, v. early scan (heartbeat and fetal pole) put my edd back 6 days, so I went with this, then dating scan at 12/13 weeks put it forward 8 days, so my due date is now 2 days earlier than the last AF date.

They do say the early scans are the most accurate way of dating, but I think when they're so early, if they're out in the measuring by a fraction of a mm it could make a good few days difference.
Like the OP said, go with the new date you've been given for now, then if you get moved forward at a later scan it'll be a pleasant surprise!