Having not played any earlier renditions of Dark Sun, it would be hard for me to compare.
I will say it came off as a harsh world, full of desert, sandstorms (with baseball sized chunks of obsidian that kept hitting us), and creatures that would attack you if they thought you had something to survive in the desert. We managed to pull some supplies from the wagon but were chased off, dragging some bodies with us.
It was harsh, it was hard, but it was fun!
Mechanically it plays just like any 4E game.