would someone 'learn' me a bit on do these poly hives keep heat out in the summer that much better and do they not hold too much heat generated by the bees?
I think most people use them to retain heat in the winter. In the summer they aren't effected by solar heat gain as much as the wooden ones, and I have notices no difference in the amount of bearding, etc that would indicate heat issues. Granted, I am not in the South where it gets extremely hot, but we do get a few 90+ days. I do notice 25-30% less honey consumption during winter compared to wood.
Also, I would think they would retain condensation much more, or is there a 'trick' they have have to resolve that?
They do, and the trick is to make sure the top has a higher insulated value then the walls, so the condensation happens on the walls and runs down and does not drip on the bees. That is also a major issue with the traditional Langstroth design (assuming you don't put upper ventilation to allow condensation and heat to escape), you get the cool air space above the inner cover where condensation takes place, and if there is enough, it drips back down on the bees.
Polystyrene hives have been used in Europe for many years and is the norm in many places.