I am frankly surprised and delighted by how close to the PS canon this actually is. This is great, and a really good sign that the fate that befell FR might not plague the rest of the settings.
Interesting Things of Note:
There is Cant: First time since 2e seeing the word "berk" in print. Makes me smile. But it is where it belongs: in the fiction.
Law vs. Chaos In Full Swing: By basically ignoring alignments, the Law vs. Chaos thing can still be in great force. Cruel Serriah's stat block says Evil, but her fluff says Lawful Evil.
4e isms Make Some Sense: The way they identified Primordials as Chaos, and how they linked the gods fighting them to the Sodkiller's philosophy of Ultimate Justice is very cool. It gives me the sense that Limbo didn't so much disappear as that the Elemental Planes disappeared.
Nilesia's Return: It's a plot hook. I like it.
4e tieflings!...but SPIKEY ARMOR!: There's no artwork of the goofy 4e tieflings, but they are described. Not a big deal. It's really cool that the art retains the distinctive bladed style of Planescape, really,
really cool.
Sigil is the Center of All again!: Arwyl is still from Toril. This could be AWESOME for linking cosmologies and having the old Planescape classic "Priest of Osiris in Full Plate with an ancient Greek Wizard and an Arthurian knight" kitchen-sink feel.
In general, did his homework nicely, lots of good fluff, didn't kill the past and take it stuff, but built on what had come before.
It took a few months, and it's only a Dragon article, but this one wins a prize.
As an aside, I just realized that Schwalb also wrote some of my favorite 3.5 books (the Elder Evils and Exemplars of Evil), so that guy's on my Watch List.
This makes me look forward to the Manual of the Planes. I really want to see what they've done with the thing.
This is good. This is cool. This makes me a content lil' banana for my favorite setting, and it bodes well for what might come in the future.
The gripes I have about 4e's mechanics don't come out in great force here, and are washed down with delightfully useful fluff for me.
This might inspire me to take back up my PS4e work, after I read the MotP...