I've quite happily used the Great Wheel in my previous Planescape & Greyhawk games but grew away from it when I started running my own homebrews. I really like that WotC is creating more "finite" sized dominions - like the Abyss, the 9 Hells, etc. rather than an infinite number of infinitely-sized planes. It's very close to what I had been doing with the outer planes in my later homebrews. I'm looking forward to the day I can put up a sprawling map of the Abyss on the wall, containing all the various fiend lords' domains in one vast, but contained, region.
And the more I think on it, the more I'm digging the idea of the Elemental Chaos, even if I'm not wholly sold the name. I'm sure we all can imagine any number of evocative landscapes/regions in it. However, for reasons I can't quite put my finger on, the Shadowfell and the ghastly named Feywild just haven't grabbed me yet. And it's odd too because I have something very similar (a slightly off-kilter alternate plane) in my own homebrew. I think I would have preferred that these two planes are natively formless, and it takes certain powerful magics to create specific and contained mirror-regions in either plane... Something about there being 3 whole mirror worlds to our own feels like it takes something away from the unique and whole nature of the prime world (if that babbling makes any sense...).