Things get "promised" (I use that word lightly), and then things get redacted. This isn't because of poor planning, it's because of the exact opposite. Good planning and development allows for agile moves and changes (infact, there's an entire discipline called Agile Development that revolves around not being stuck to what you say, but instead course correcting as the project moves forward). Greg is spot on when he says we should be thankful that these changes were rejected.
Let's talk about the elephant in the room -- flying. Why was it disabled? Well, we know in broad strokes that it's a gameplay issue for Blizzard. They want players to have a better experience when they travel around the world leveling. Was this a decision that was made by Cory Stockton waking up one night and going "Eureka! I'm going to disable flying tomorrow!" No, it wasn't. not by a long shot. It was a decision that while someone probably said in a meeting, many designers were likely thinking about it, and after the group talked it out and decided it was a good course correction, it took place and was announced.
Blizzard has some absolutely rock star designers and developers -- I have no doubt that they tested leveling with flying. They had to in order to draw the right conclusions (and remember too, we know what leveling with flying is like, given the previous expansions). People might not like the change, but it's not because the designers are idiots and break promises. It's because they're iterating over game design. It's what we desperately want and need them to do. After all, we don't want to end up with another end-game like we had when Cataclysm was released, do we?
I'm not saying you need to agree with everything Blizzard does -- you don't, and I certainly don't. But it is important to recognize that these changes in course are normal and good.