My love is tough
The City of Brass excerpt is better than earlier excerpts from the 4e MotP, I'll grant it that, and it's not bad at all. The map is very similar to the map as depicted during 2e and 3e (its a redrawn version of the 3.5 PlHB map), and the map is probably the best thing in the excerpt. Everything else is generally similar to the material from the 3e MotP, 2e Planescape's 'The Inner Planes', and Al-Qadim's 'Secrets of the Lamp'. It's just an overview, but there's nothing that utterly clashes with earlier material, and a lot of names and places get recycled (which I would have done in the same position). A few 4e'isms get mixed in like archons, which while a tad odd, it's nothing majorly clashing in terms of previous flavor.
I still think the level of detail is on the light side, but what's there isn't bad. Of course I can't really make an unbiased comment on much here since I wrote up the City of Brass as it exists within Paizo's Golarion/Pathfinder cosmology within the last month here. And honestly, I'd appreciate any comparisons and critiques looking at my own take and WotC's take on similar planar topics once the 4e MotP and Paizo's The Great Beyond are both released.
That said, my only real complaint is a general comment on the 4e core cosmology's Elemental Chaos: the thematic flavor and atmosphere of the elemental chaos seems schitzophrenic to me - do you represent a fusion of the elements, or do you represent the unformed chaos of limbo? The flavor seems to switch back and forth, uncertain at times if it's going to try to model itself upon the earlier conceptions of the elemental planes, or crib upon the 1e/2e/3e notion of Limbo. It's combining a lot of concepts that compete for attention, and it can't make up its mind which one it's trying best to be. I'm not sure how that's going to work out - but as I said, that's the only major complaint I can come up with for this particular section.