Here is what I have learnt.
On the negative side
It has taught me just how much man can destroy enviroments and habitats that some of the most amazing fish come from.
It has also taught me that mass breeding in the far east can lead to some very poor fish strains and mutations of species just to make them more commercial for less experienced fish keepers.
On the positive side
It amazes me how many completely different weird and wonderful species there are out there.
Also how dedicated some aquarists and hobbiest are to the hobby eg. The British Killifish, cichlid and Livebearer Asssociations.
It has also taught me that there are fish shop staff and aquarists that Know very little about fish, although they think they know everything about everything. With saying that there are shop staff and aquarists that I have a great deal of respect for as they know so much. So to some this up I think I can say it pays to listen to advice. Although you have to decide for yourselves how credible the advice is before you act.
Fish shows are a good way to see what fish other people have.