I have played in Eberron and run a session of Eberron. Playing in the setting was mildly interesting, but running it was godawful. I'll admit to not liking the setting before it arrived. I bought the book when it came out and I found a lot of impressive points. I really enjoyed the Great Houses and there seemed to be a lot of flavor feats, which did not crop up in normal D&D that often.
After actually playing in the world, I was very unsatisfied. It does have a kitchen-sink feeling to it. The parts do not always mesh together well either. Their seemed to be a lot of scifi/superhero aspects to the world such a robots (warforged) and mutants (shifters/changelings).
The biggest problem with the world is that it uses everything from D&D. This means that it incorporated ALL of the power creep in the splat books. While this may be great for some people, I am not sure the setting can fit everything produced for the game and remain viable.
I certainly enjoy some aspects of Eberron, but those aspects can easily be ported into a homebrew. For me, it is the restrictions and theme that sell a setting. Midnight, Dragonlance, Planescape, Dark Sun, and Ravenloft all had aspects that grabbed you and made you want to play in that setting. Eberron has some cool ideas, but nothing grabs me and says that I must play here. On the surface, the setting seems unique and different.
After playing and running the setting, it feels very cookie cutter with a lot of kewl powers thrown in. It has potential, but as long as it incorporates everything regardless of how appropriate, then it will fail for me.