FWIW, with a lot of the questions, I see it as a continuum.
Were demons and devils the same? Not really. Is it still cool to make them more different? Yes.
Were the good planes boring? My campaigns say otherwise. Is it still cool to make them more exciting? Heck yeah.
So I'm supportive of the design team's efforts there.
I guess with the 4e changes from "Planes of Instant Ouch" to "Planes to Adventure In," I'm just an unabashed fan.

Awesome alien places to send my heroes without the need for high-magic weirdness is neat, and I'm glad 4e supports this more. Could they have preserved the original energy-like planes, too? Sure, they could've. But if it just boils down to fluff, what's the big deal?
I guess the main question with that is: what about these inhospitable planes was appealing to you when you were playing the game or designing the world? Why did you like a Plane of Only Fire? How was it useful to you? What did you do with it? And what can't you do with it now that it's a Plane of Elemental Chaos that you could do with it then?
The Little Raven said:
Yes, it gave me small areas, while the rest of that plane was an endless sheet of fire that is worthless to me and the games I run.
...
No, because I would still have a book with a ton of stuff that is useless to me. That's not me getting what I want
Well, on the first point, people seem to be saying that it's OK to have places in existence where the PC's can never really go (unless the plot calls for them to and thus gives them Plot Immunity vs. that place). It's OK to have a big empty field of fire because the PC's don't need to go there unless they're being burned by their enemies (in which case, all it needs to do is damage).
On the second point, because those planes aren't meant to be adventured in, you don't need a lot of stuff about them. You could just have an entry like:
Plane of Fire: This plane is inhospitable to most mortal life. It kills creatures not completely immune to fire. Its only inhabitants are rumored to be creatures made of and immune to fire who see it as a paradise.
And then move on to the more interesting places.