Given that I am a real estate agent, it's difficult to answer this question without looking biased. But you asked, so here's my opinion...

Yes, you should be represented by an agent if you are buying a new home. And no, I'm not saying that just because I'm a real estate agent...

Consider this. That smiling, sharp dressed young man or woman that greets you in the builders office is a licensed real estate agent. Who do you think they work for? The builder, that's who. Who's best interest do you think they have in mind, yours, or their employers? I don't believe I need to answer that for you.

No, the builder's agent won't cheat you. But they certainly aren't going to negotiate for you. You're not going to save a nickel by representing yourself, and the builder pays your agent's commission. So why not have professional representation from someone working for you and your interests?