Yeah, it was sweet. From what I understand it was made for the contest that Eberron won, coming in second, but that could be hype. I've almost enjoyed just having a core rules with only me and the players creating new things as needed and based on play rather than trying to work in a continual set of new rules and powers each time a new book came out. I've run two 3.5 campains in that world now and enjoyed every minute of it.
Personally, I think I'm going to try to use the world and history for a 4E campaign. The world already has Tieflings, make Eladrin be Dawn elves and 4E Elves be the Night Elves, add a kingdom in the Tamerland of Dragonborn who rule over Lizardmen, and all the core races are there without much work. With a dynamic of increasing power and selectable power as you level up already in 4E, you know it was a good idea when they did it for Dawnforge and wonder if FFG should be looking into where the 4E development ideas really came from
The concept of immortals vs gods and legendary monsters are all flavor a good DM can work in. Action points replace legendary points, pargon paths and such replace legedary classes, and you can work in highly magical areas for magic wells with work, like natural feywild areas etc. It's strange how many of the downforge ideas seem to be like some of the 4E play concepts.