Never Trash Your Competition
I'd imagine in every submarket of every MLS of every area of the country, there are agents who have built a reputation of questionable ethics. You might have had a bad experience with one or just heard about them through the agent grapevine.
Even though you might relish the idea of letting someone know how you feel about the agent, don't do it. First of all, it's very unprofessional and even if what you're saying is true, trashing your competition diminishes you as a Realtor. But there's another reason you should consider, it might be a setup.
I remember one listing appointment where a seller kept redirecting the conversation back to another agent they said they were also interviewing. They kept asking me in different ways what I thought of her as a person and agent. It was very odd but I responded as I always do.
I said "Yes, I know the agent but don't know much about them or how they work. I'm sure they'd do a great job for you too". Then I redirected the conversation back to what I was there to do, explain the great services we offered.
Not surprisingly, the other agent got the listing, but I'd handled the situation the right way and didn't have to worry about the seller telling the other agent I'd trashed her. Remember to always take the high road. Cameras are everywhere and you have to be just as careful on the phone.
If you don't get the listing, be gracious. Thank the seller for the opportunity and let them know you'd love to talk to them again if things don't work out with the other agent.