Plane of Shadow + the apparently new (to me) cosmology

You didn't? That's strange - it was there. It was called the Demiplane of Shadow then, but there was quite a bit of detail on it in A Guide to the Ethereal Plane, and in one form or another it's been around since early 1st edition (it was described in the appendix to the original Deities & Demigods back in 1980).

Spells like Shadow Walk, Shadow Monsters, Shadow Magic, Shadow Door, Demi-Shadow Magic, and Demi-Shadow Monsters - any illusion spell that creates solid material - have been based on the Plane of Shadow forever. Those are major spells that were in the 2e Player's Handbook.

Monsters like the shadow dragon and the shade come from the Plane of Shadow. Again, this has always been the case.

It wasn't considered a full plane in 2e (although it was in early 1e), but it's always been a major part of the AD&D cosmology. It's really weird to me that you wouldn't know that, if you had any familiarity with 2e at all.

You could do it with a spell key. It creates pseudo-elementals rather than true elementals, but the effect is the same. I'd still use this rule.

I wasn't being sarcastic. At any point. I was just surprised that you apparently hadn't heard of the demiplane of Shadow.

Again, not being sarcastic. That was my honest impression. Apparently I was mistaken.

There you are, then. It's the same thing.

You can understand, then, why I'd be surprised that someone familiar with 2nd edition wouldn't have heard of it.

No apology necessary for asking the question.

I didn't expect you to have necessarily read the books I cited. I was just noting previous descriptions of the plane, because it's hard to talk about why changes were made without noting previous changes.

I imagine they made it a full plane in 3e because it's so fundamental to the way so many spells work. It had been a full plane in early 1e, too.

No, everything "floating" in the astral plane is the new default setting. Eberron has its own unique cosmology, as does the Forgotten Realms (but I hope that most people pretend this isn't the case for FR) and some other campaign settings. It's not hard to ignore it; but I prefer it to the old cosmology. It's not really all that weird at all.

Moog, don't worry about asking questions. No matter how many you ask, you've still got a long way to go before you catch up to me.

Also, Planescape assumed that the planes were the same for all settings, with each setting taking up a different crystal sphere in the Prime. 3/3.5e WotC assumes that each setting has its own cosmology with its own set of planes, the default of which (described in Manual of the Planes 3e) is similar to that of Planescape but with less details fleshed out (left up to the individual DM's) and some major connections changed, such as the Astral being ubiquitous, the Plane of Shadow becoming a transitive, and the Inner Planes being only six in number (to name the most drastic).

I really don't see this as much of a big deal. I prefer for all of the DnD settings to be part of a unified cosmology; so in my campaigns they are. The goal of WotC's changes was to put control more firmly in the hands of the individual DM's. Of course a DM was always free to make whatever choices he wanted; but these new changes force them to take control into their own hands so as not to use much of the crap WotC puts out (example: Illithids from the future who arrived in our timeline 2000 years ago).