Brain asplode...where to begin ?

WotC material: start with the Manual of the Planes. It's watered down Planescape in many ways. They removed all the para and quasielemental planes in the name of simplification. They expanded the plane of shadow in an unexplained inverse of that. They made the Astral overlap every sodding plane (taking over the role of the ethereal). The ethereal in WotC's interpretation has a bunch of ghosts, straddles the prime material, and really has little to justify being a transitive plane, being as how it doesn't go anywhere.

The flavor of PS got stripped out.

The WotC monster manuals have done a decent job of converting monsters, though they've ignored a lot of Planescape material in the process. The yugoloths lost alot in translation, and the gehreleths got renamed demodands (and their origin myth ignored).

WotC's Planar Handbook. This book knoweth no end to the meaning of 'this blows'. They tried to recapture the flavor of Planescape (with faction prestige classes, etc) and failed most miserably. Planescape pastiche. Throw out everything except possibly the sections on Sigil, the City of Brass, and Tunarath. (Sigil, if bland, doesn't contradict much previous material, or Planewalker's stuff. Ignore WotC claiming The Lady is LN) The last 40 odd pages of the book are wasted on what amounts to nifty planar sites where you go, kill the monsters on the associated random encounter chart, and get powerups to justify your PCs' going to the planes to kill stuff. Utterly at odds with what Planescape was, best to ignore it.

Here on Planewalker: In the official releases, we've put out a number of chapters on everything from Sigil (In which I top WotC's Planar Handbook effort by a factor of ten at least), the Factions, Races, etc converted into 3.x stats. Keep in mind that anything of ours is assumed post Faction War.

While your new Planescape material is good, I'm afraid I won't be using the Sigil chapter precisely because it takes place after the Faction War. As I've said elsewhere, I don't find the new Sigil with the neutered factions to be nearly as compelling as the original. Nor does it have as much fluff material to support it as the whole Planescape line.

You may want to consider a Sigil chapter written from before the Faction War, for those people who still play old-school. Otherwise the new fandom will continue to be split.

To update it to 3.5E and to make it available for free on planewalker. Sure, you can use the old material, but a lot of people don't have access to the old material, don't want to pay for it, or simply would like to see an update that doesn't necessarily destroy the structure of Sigil as presented in the original material.

I wouldn't presume that someone who wants to play planescape knows enough to differentiate pre- and post-Faction War and would go buy the Guide to Sigil. Many people don't even know what that means. They simply want to play Planescape, but with 3.5E rules. It's confusing to newcomers to Planescape who have heard of it, maybe even bought a book or two from ebay, to read the PSCS chapter on Sigil and find that everything has been thrown upside down and is now incompatible with the older books.

I thought that the pre-FW vs. post-FW discussions were over...

Anyway, I'd hoped that pw.com would do what SWRPG did. They published three mini-settings in one, the "Rise of Empire" era, the "Rebellion" era, and the "New Jedi Order" era, using the same rules.

The final version of PS3E could be done the same way, letting everyone choose whether to play pre-FW or post-FW.

But then, it would only take a little extra effort by the DM to ensure such a game is possible with the current system the way it is anyway .