Anyway, hard core Dark Sun fans may point out problems with my summary.
Hmm, except for a few minor points here and there (like the fact that technically, all of Rajaat's Champions turned Sorceror-Kings were actually dragons, each in various stages of developement; Borys was the only one to have completed the metamorphosis proccess, a proccess that drove him mad for hundreds of years whereupon he ravaged the lands even further with his potent defiling and rampant destruction. Some sources cite Borys as being responisble for the Sunrise Sea turning into the Sea of Silt.) your overview was on the spot.
beyond that it seemed like a fairly typical high fantasy setting.
The only true look at the Green Age and what life was like then comes form he Mind Lords of the Last Sea supplement. The picture painted there implies that the Green Age was different from standard fantasy by the prevalence of psionics and the unique nature of the various 'normal' races even during that age. Granted, its much closer to standard fantasy than the Athas after the Clensing Wars.
I've often debated trying to track down some of the later supplements just to see how they finished shaping up the world.
Some are worth a look for their continued twists on the established norm (just as the innitial products were a twist on standard fantasy at the time, the revised line of products were a twist on the innitial products), others are simply full of jumbled garbage or glaring pieces of trash that overshine the rest of the product. For example, Windriders of the Jagged Cliffs, while very divergent with its look on the ancient halfling decendants and their use of organic technology (called lifeshaping), its a good read with plenty of great ideas. Others, like Mind Lords of the Last Sea are mostly good, but contain such trash as surfing druids and stereo-typed 'remnants' of the standard races (mountain dwelling dwarves and forest dwelling elves, but then even stating that these were not the norm for the Green Age). The book Defilers and Preservers is nice, but Psionic Artifacts of Athas creates some serious continuity errors. Thri-kreen of Athas is perhaps one of the best 'racial splatbooks' you'll ever come across for any setting. A must have for any Dark Sun gamer.
Also before the revised Dark Sun boxed set, the Blackspine adventure implies that psionics on Athas started due to a failed Githyanki invasion and a psionic weapon that mutated all the races on Athas in distant past.
The implication is that the 'mutation' was of a mental kind, not a physical one similar to the Rebirth (when the ancient halfings, called rhulisti, mutated themselves into the various sentient races of Athas), thus enabling most every species to utilize psionics of some kind. Its generally not accepted much as a major issue of canon, but some stick with the idea.
But something went wrong and the sun began to change from blue to yellow.
The something was that the rhulisti attempted to alter the nature of the oceans themselves, to change them in a way that they produced even more food than they did previously. They failed and created what is called the brown tide the swept over the oceans killing off anything and everything in its path. The rhulisti used the power of the Pristine Tower, fueled with the energy of the sun to destroy the brown tide. This act of tapping into the sun with the Pristine Tower is what caused the sun to change from blue into yellow and caused much of the planet's oceans to recede, thus ending the Blue Age and begining the Green Age with the Rebirth.