I loved the 1e version of the Great Wheel. The 1e Manual of the Planes is, in my mind, one of the best RPG books ever written - and certainly in my top 5 best D&D books ever.
With that said, most of it was unusable in my games. In fact, I know that I never used it. Still, it was fascinating and wonderful, and made every plane - even the potentially boring ones - interesting.
I also loved the BECMI/RC planes. There was a lot of cool stuff there, including very interesting discussions of planar dimensions. It was completely fascinating and alien, but again, I never used it.
On the other side of the coin, I just never got into Planescape. The setting did absolutely nothing for me, so I mostly ignored the Planes in 2e and 3e, except when I couldn't. (The only planar adventure I ran, as such, was Expedition to the Demonweb Pits. I ran an other-planar Arcana Evolved game, but it wasn't related to the Wheel at all.) It was good to open up the planes to more adventuring, but without the inherently hostile environments, it did nothing for me.
I'm also mostly ignoring the 4e cosmology, but it works better for me than the Planescape wheel. I love the Feywild, like the Shadowfell, like the Astral Ocean, and am ambivalent about the Elemental Chaos. Again, I don't expect to run many planar adventures, so it's no big deal to me. Still, I get the sense I can cram whatever I feel like into the framework, so it will work just fine!
-O