I'll agree with Alysse that you should have your interests protected by having your own Buyer's Agent, but it doesn't have to be an Exclusive Buyers Agent in my opinion. Your questing is plain and simply: What's the quality of the builder?
I don't know anyone who can answer that question with a broad brush other than the principles (buyers) of a transaction in the neighborhood you have interest in. Problem is that things change per location and even as a neighborhood gets built out. Just because someone had a great home built doesn't mean you can let your guard down and have blind faith that you'll get the same.
I've been in the custom home building industry for 28 years and have seen and heard it all. Frankly, there aren't many agents who know what to look for in terms of problems during construction. What you might want to do is to work with a Buyer's Agent (you can get representation without any "out of pocket" costs to you) who can help you review the design and specifications differences and make selections that suit your needs and budget.
Then the next hurdle is getting terms for when the home completed that you can live with and that you understand so you don't loose any mortgage rate locks. A knowledgeable Buyers Agent can provide additional inspections of the home during construction so that any shortcoming can be address by the builder as they are identified. These inspections might even involve a 3rd party inspector, but if the agent's knowledge is broad, their insight can be invaluable. Catching problems early is a key to getting a good home. Keep in mind the builder wants you to become a satisfied member of their new neighborhood, so they should be doing their best to produce a high quality home and they should be responsive to your concerns. My last client that I represented appreciated the advice they got on design, terms, material selections, mortgage terms and timing for rate lock and inspections which found problems that the builder responsibly corrected. Your best bet in discovering how others like their homes would be to visit the neighborhood on the weekend when other Toll Brother home buyers are out and about. Ask them how they like there homes and neighborhood. Also ask what they might do different.
Best of luck and keep the questions coming. Feel free to contact me if you want to talk in private.
Greg Hanner, Broker, REALTOR, e-pro