No Great Wheel in Pathfinder...

Btw, the original name of the Plane of Pure Law was "The Clockwork Nirvana of Mechanus."  So it's actually pretty old-school.  :^)

And since a lot of those are real-world myth, they're legit!  :^)  I also love "Concordant Opposition."  Though I trust "Happy Hunting Grounds" will remain quashed.  It's a bit on the insensitive side.  IMO.  Perhaps "Primordia."  Or "Eden."  ...I like Eden.  A plane representing the state of innocence that comes from animal simplicity.  Heck, all of a sudden I'm liking that better than "Beastlands."

You came here unarmed?  Well, grow some, quick.  Sure, this is the plane of unspoiled nature -- what does your religion call it?  Paradise? Prelapsaria?  Eden's a common one... right, then, Eden.  Yeah, this is the place: life as it exists untouched by evil.  Some say it's a preserved remnant of what could have been had evil never tainted some glorious vision of the first Creation.  Some say it's the template that the good Creator gods use for new worlds, the best possible state of nature.  But whether it's just the state of affairs on the Prime Material, or constant interference by Evil, nowhere else is quite like this, and that's why I defend it from clueless sods like you. 

And defend sods like you from it.  See, just because Eden ain't evil doesn't mean there aren't things like pain and fear here.  There's no death, leastways not for the petitioners as long as they care to stay.  But paradise for some of these creatures is the hunt and the feast, the fight for status and territory.  What, you think lions spend the afterlife eating coconuts?  They're predators.  But even prey that gets caught just pops gets reborn to parents somewhere else on the plane.  Yeah, there's sex here too, what kind of paradise did you expect? 

Anyway, there's enough of the problems to make the good parts of their afterlife sweeter.  Things just work out for the natives without them thinking about it, they just end up in the right places.  But us living sods running around thinking about things too much, we're not in our place here, and we can be prey too, for real.  So... I've got a spare bow.  How's your archery?

The planar landscape of Pathfinder isn't a copy but rather along the same thematic lines, in the same way I'd use Beyond Countless Doorways as a reference for PS over a lot D&D material...though I've been pleasantly surprised by some of the stuff in the "magazines" WotC is putting out.

Thematically Pathfinder and PS parallel each other. Gods hold realms in the Outer Planes and interact more directly with the world, the elemental and energy planes exist along with the Ethereal. The Outer Planes and Outer Sphere are kissing cousins, and despite the at times confusing name switches it's easy to see where you can take something out of Pathfinder's planes.

Even daemons quest for oblivion, while a different take on NE, can be substituted for the loth's goal of the final triumph of evil. That said, I'm not wholly convinced daemons are easily ported into the race of yugoloths but I think that's more of a case by case basis. I could easily see Pharasma, Judge of the Dead, in Mechanus since that's where On Hallowed Ground placed the Hindu psychopomp Yama.

Really though we'll have to wait for Shemmy to give us The Great Beyond before we can make any final judgments regarding compatibility.

Shemmy, will we get more on the motivations of the respective fiendish races and as importantly the celestials? WotC really dropped the ball with regard to both of these facets, leaving us with handicapped articles on Abyssal Lords...just how many times can we see "all demons are barbaric murderers, but this guy takes it up to 11"?

Really curious about the elemental factions as well, glad to see legitimate planes there.

I always felt that something better should have been done with a race of chaotic exemplars.  The Modrons fit in perfectly as lawful exemplars being based on geometric shapes, but I always felt a chaotic exemplar race should be, well a little more fluid or formless in shape.

I know they suggested the ancient primordial Slaad were that way, but as toads WotC never did much to distinguish them from the Tanar'i in many cases.

First off, you'll notice a common thread in all those names.  Those are all names that are pre-existing in the public domain, and thus legally they are not WotC IP.  Thus why the terms "Tarterus" and "Nine Hells" are used instead of "Carceri" and "Baator", respectively.  That's why, I assume, nothing mentioning Mechanus or Bytopia are listed in there.  The idea of a plane of mud and lightning are also already generic enough that legally they couldn't be WotC IP; this is why they made no attempt to keep the elemental and energy planes out of the SRD, I can guess.  Further, in fact, the idea of alignment-based outer planes for all alignments are in the SRD.  The idea of an LG plane is in the SRD, Mount Celestia specifically is not.

A question, since I haven't read Tome of Horrors yet myself, I have to admit: how much information that definitively refers to things from the WotC conceptions of the planes listed are given, things which are definitely not public domain in any fashion?  For example, the idea of the Nine Hells in general is on the surface just Dante's hell, so the idea of an LE hell plane with multiple layers and whatnot is public domain, as are the city of Dis, Asmodeus, and other mythological figures and locations.  The Pillar of Skulls is not public domain, because it was a unique creation and thus part of Wizards' IP.  The City of Brass is mythological, and thus public domain.  The City of Glass is a unique creation and is not.  How much in Tome of Horrors falls into the "unique creation of WotC" category?

Edit: Thinking about it, I realized that this might sound a lot more confrontational than I intended.  I'm not trying to bash your claim or anything, I'm honestly curious about the answer to this.  Especially because it can get really confusing what with how much of D&D's planar flavor draws on the public domain.  I hope this didn't sound too much like an attack on you, I was just asking for clarification is all.

That's the long and short of it, yep.

And that sounds like an interesting direction, how you described Necromancer Games.  I've heard good things about them before, although never in much detail.  Hearing their "mission statement" as it were like that, I'll have to keep a wider eye out for their work now.