Pros: If you're going to do your open water diving in Koh Tao, I do recommend them. Professional, friendly, they gave my boyfriend 1-to-1 instruction on his Open Water certificate. They also gave us a discount accommodation (at Silver Sands resort Bungalow next to Sairee beach). They have a small pool, where a lot of people do their open water. The restaurant served pretty good food. It was cheap (not really spicy).
Cons: The diving in Koh Tao Sucks. Visibility is low, not colorful. The tiny boat that we were packed into was almost sinking because there were too many people on it. There's nothing really bad about the dive shop itself except for overcrowding, but if you are going to do your Open Water, there's better (and cheaper) options than Koh Tao, such as Semporna in Malaysia, Sabang, Phillippines, Kota Kinabalu Malaysia (also bad visibility but a little bit cheaper), and Koh Lanta in Thailand (more expensive but the visibility is phenomenal)