While is is critical to work with a realtor whom you trust and truly understand your needs and preferences. At the end of the day, it's your money, financing and investment that is being made for what is most likely a very large investment on your part.
In my experience, I have dealt with agents that come in many shapes and sizes. Some will tell you what you want to hear, but most have your true interest at heart. Even then, we may not get it 100% right. This is why I strongly suggest that buyers should seek out advice and information about a property and location prior to making that initial offer.
For example, i have lived and worked in many beach communities in North Florida as well as the Miami area and South Beach. I have learned that it is not just knowing your market inside out (which is critical), but knowing your buyer as well as others who may know your buyer(s) before making that offer. They can be a factor in shaping the decision making process (even for the most educated buyers).
In summary, I believe that all realtors want to see a happy customer for both the buyer and seller. Buyers today have plenty of data to conduct research and bet the process started. It is up to us to make sure that what they see is truly in fact what they want and is best for our customers.