Meh, the house we bought was overpriced, we gave a lowball offer ($50k under), did a little horsetrading with the owners who were motivated to sell, and came in at a final cost $30k under asking. It depends on how hot your area is and how motivated you are as a seller.
ETA: and they had just put in a new kitchen and bath, which made us interested, but not fiscally wanton.
ETA2: it had been on the market for a year (!) and had already come down in price, so that told us we could negotiate. Two weeks doesn't seem like that long. Ask the realtor the average selling time for your neighborhood. For example, now where I live houses sell in days. Offers come in before the open houses.