@Centrals, again, it's great that you have figured out a system and found an operator that works for you, but if you had used a good agent, perhaps you would have been spared the bad dive you had to the King Cruiser when you booked with the operator directly? You have some preconceived notions which appear to be colouring your advice here, and I think it must simply be due to your lack of understanding of how the dive industry works on Phuket. I'll try to explain a little, since you ask.
Since you have never used an agent, I guess you don't know that we are not "middlemen" in the sense that most people interpret the term. Divers pay no more when they use the services of an agent than when they go directly to the operator. It is the operators who pay us to bring them customers, and we agents have excellent working relationships with the operators we represent. The operator that doesn't encourage and welcome agency bookings is extremely rare.
You ask how we obtain the knowledge so that we can advise our customers? The operators do everything they can to help us! When a new operator opens, they send us emails with schedules, announcements, etc. Operators send their booking/marketing managers around to our offices at the start of every season to drop off materials and make personal contact. They hold events on their boats to get us on board for a look around before sales to customers even begin. It's a close and supportive working relationship between the agents and the operators.
How do people find agents? By looking in places like ScubaBoard. There are numerous positive comments about several of the agents who work here on Phuket right here in the Thailand forum--these include Ringo, Stevenl, and me.
Centrals, you should book with your favorite op and research your options in the way that suits you best. I'm glad you come to dive with us from Phuket, regardless of how you book. I am responding to your posts simply as a way to fill in gaps in the advice you give to others, and I'm honestly not trying to get into any sort of debate with you. I'm only saying that your way isn't the only way even though it is the best way for you, particularly and individually. The fact of the matter is, however, that your way is not the best way for everybody, and actually it's not even the best way for most people.