I'm one the fence on whether I'd go the realtor route for a new construction home or not, as not using one would lower the price of the sale significantly because the builder would discount the property by the rate of the realtor commission. I'd like to talk to a really good new-construction realtor to see where he/she might be able to provide me that value, as overall it would be a lot easier with a realtor.
I would likely use that same realtor to sell my current home as well if I go that route.