So a game system that says "x station imports widgets" but when you get there you find that it has a high SUPPLY of widgets is working fine then? What a lot of the "trading is fine you need to learn how to trade" crowd are missing is that many of the players that are complaining about broken systems (like myself) know HOW to trade, it is the fact that the game information is simply wrong.
I like the idea of the trade routes drying up and others opening up but I should not be having to go to out of game sources like slopeys to find my next route because the in game presented information is plain wrong.
It's possible that what you're seeing is that some systems BOTH import and export goods by design. This seems to mean that at a given station, you might find a certain commodity that is imported, exported, or both, not necessarily that it is always both imported and exported. A good example is that all agricultural systems can import and/or export several types of food.
A good resource (not perfect, but good) is this Trader's Bible chart:
http://i.imgur.com/ang1e0I.jpg
It shows an overview of types of stations, and what commodities they import and export by default. It's no longer 100% accurate (mineral oil doesn't come from agricultural stations, but now comes from high-tech, for example) but it's been a very valuable reference for me.