I noticed no one had ever replied to this post so I thought I would offer my two cents.
Obviously when you first posted this question, the real estate market for builders was a bit different.
Now, here in 2008, the landscape has changed. Here in Minneapolis, we have a large supply of homes, condos, townhomes for sale on the MLS. Buyers are surely out there, but it is taking much longer for homes to sell. In regards to builders, I know the market has been extremely challenging for them.
Here in Minnesota, we have worked with a number of builders over the years helping them sell their homes. I personally have always liked working separately from the builder. This allows an agent to do multiple things: work with investment property buyers and sellers, list short sale and REO properties on the MLS....
Instead of just selling directly for the builder.
Of course I know many agents that are extremely successful who work directly with the builder. They generally have a small base with commission. Again, this has changed somewhat however with the market.
I hope this information helps. Have a great day!