I have to say, I'm not happy with this path for Pathfinder. Just as 4e starts to win me over, Paizo is knocking the wind out of my sails. 4e is going for revolution in the ruleset, and Paizo is going for evolution... Okay, might work, but...
I've looked over the ruleset. It's 3.5+ (3.5 + 0.15 + a little bit of broken). There's just not a whole lot there that makes me go: "WOW, you've solved it!" It's also clearly *not* going to be backwards compatible, regardless of how it's advertised. The skill names have changed, the races are stronger, the classes are stronger. If you're writing adventures for level X characters in the Pathfinder RPG, level X 3.5 characters are going to be underpowered.
The 15 minute adventuring day cannot be solved by simply giving the cleric more healing. And using TURNING (1d6 healing to everyone)? That's essentially giving the cleric mass cure spells in the early levels. Why bother with cure light wounds at all? Massively overpowered.
Not to mention the fact the undead just won't stand a chance. Do damage to them and heal your party at the same time? Gee, that's a good option.
Wizard get d6 hps/level. And essentially domain spells. Which takes away from the cleric's flavor and makes wizards overpowered as well.
Fighters get more plusses, and weapon groups (the lack of weapon groups in 3.5 was idiocy, so that at least was a good change, if an obvious one). But it doesn't nearly make up for wiz and cleric.
Barbarians get... wait what? No barbarians? So, the cleric gets like 6x more healing, and the barbarians get nothing? Same for ranger, druid, monk, bard...
Keeping +2/+2 skill feats? Really? Lame.
Do we really need taste/touch/smell modifiers codified? Does ANYBODY actually care what the DC is of tracking 4 people when it snowed yesterday? Or the DC of seeing someone 200 feet away? Here's an idea: Obvious - DC 5. Noticeable - DC 10. Faint - DC 15. Subtle - DC 20. Deliberately obscured - DC +10. It's these sort of anal details in the 3.5 rules that make some DMs drool over the reports of 4e.
The Pathfinder RPG can replace the core rulebooks, sure. But now consider all of those other splat books you have. Want to take a prestige class? Well, think again because there's a good chance that the now more powerful base classes are going to be a better choice.
The main positives changes I see are: attempts to fix hp/level, weapon groups, skill merging, and attempts at fixing grapple (CMB). But it's all very house rulesy. Most of the changes are things that could be individually done with simple house rules in 3.5.
If you're going for the bazaar vs. cathedral, you could wikify your alpha'ed ruleset, but you'd really be counting on the wisdom of crowds. Iffy, but hey if you're going to shoot for the stars it's one way to get buy in, and potentially good rules.