Top dive gets mixed reviews. (you can go to tripadvisor.com and read the reviews) They are by far the biggest dive op in French Polynesia with locations sprinkled though out the most popular islands. Business is business no matter what part of the world it takes place, when you get big, you get big at a price. Sometimes you'll hear them described in less than favorable terms in regards to the baggage that comes with a bigger operation>> less personal service/attention, being more of a slave to a schedule than to the joy of diving, hit and miss depending on who the dive master is on the dive,, diving the more tame dive sites due to the average lower experience of their dive clientel, etc...
As I said though, a lot of this stuff is stuff that is invisible to the new diver, to the more experienced diver, they've been there, done that and are looking for a more 'advanced' and more personal dive experience and often shy away from big, impersonal dive operations. Being a new diver you will have a great time with them, they are safe and competent and sometimes being new, the 'dumbed' down version is safer especially in Rangiroa, where the dive conditions are more complicated, believe me, the worst dive you go on will likely still be one of the best dives you've ever been on.