Shemeska
Adventurer
You know, this might be the second 4e book that I buy just for the details on Sigil. Unless they hack it to death.
I'll take a look at it in the store to be sure, but I'm not honestly sure what to expect. Given 4e design focus thus far, I'm worried as you say that it might be hacked to death. I'll give the authors the benefit of the doubt, though I'm not aware of any of them having worked on anything planar (except for Laws co-authoring FC:II, which wasn't bad).
I'm surprised that Schwalb wasn't brought in to help on the Sigil writeup, given the really good job that he did with the City of Doors, and some of the factions in a DDI article on the Mercykillers. If they hold to that level of quality I'll be very happy, but again given how 4e has handled previous planar concepts so far, I'm still leery.