I dove with them on 3 separate one-day trips just this past September; my avatar photo was taken on one of their trips.
Like scubashooter said, they are a great outfit. For a "cattle boat" they provided excellent service. The boats are nice and spacious, and the food was good. Their dive leader-diver ratio was no more than about 1:6, but if you have your own dive buddy and hold a minimum basic O/W cert you are not obligated to use a dive leader (which they do charge extra for). They provide 65 cu. ft tanks but if you ask they will provide an 85 at no extra charge.
If you are staying in Cairns they will send a van to come pick you up and drop you off.
The only caveat is that they do cater to a lot of Japanese tourists, and you might get stuck on a boat where you and perhaps a couple of others are the only non-Japanese speakers. The Japanese crew do speak English but it's of varying quality, however if you are put on one of these boats your dive briefing will be done by someone proficient in English.