I have worked with many, I mean more than 10 real estate agents, but only a couple of them can be classified as reliable. The agent takes care of himself first, then you. Some of them are smart enough to know that it is his long term interest to take good care of his client, but many more just want to make the money now, and don't care the future.
As an investor, you should judge by yourself if it is a good deal or not, not by your agent. Your agent will be more than happy to buy and sell for you to make the money, but you need to make sure he or she provide the quality service you need. I usually find the deal myself, ask the agent to let me into the house, and submit the offer for me. Most of the times, my agent does not even go to the settlement. For this reason, he or she usually kicks back half or even more than half of the commission as closing help.
But if you are not familiar with the market and the buying process, you need a good agent. A good agent is not cheap. She or he may insist to have all of the commission. If he or she can save you tens of thousand dollars, then s/he worth it. Of course an agent always wants to make the deal happen, but by the same time, s/he should not mislead you.
For me, lots of agents ask me if it is a good deal or not when they want to buy for themselves. I can only judge by the current market as I do not have the cristal ball to predict the future. Including the two houses I sold, I have bought 11 properties for myself, and helped to make the decision for my brother. Among all of these, I had two bad decisions as the current market price is lower than the price I bought, two average decisions that I make only a small profit if I sell now, and the rest were very good ones which means, :-)
Buying or selling a house is one of the most imporant financial decisions in your life. You should take some time to study the local market carefully to avoid paying too much or selling for too less. Do not be fooled by your agent. By the same time, if your agent is a good one who takes care of you, then listen to him/her. Usually, s/he knows more than you do.
Fortunately, I have a reliable loan officer who gets me good rate most of the times. As I have so much debt there, it is hard even to have my loan approved.