Not very at all. Essentially, it is 3.5, just with some changes and new content. What's really great about it is that all of its content (as far as I know) is available for free here: http://www.d20pfsrd.com/
A lot of the changes involve related skills being combined (like hide and move silently becoming "stealth") and balance changes, with some feats being weakened a bit, and weaker classes like fighters and monks getting some nice upgrades. Another cool thing about it is that spellcasters can use 0-level spells all day long. Anyway, if you're interested, you should definitely read through it and get familiar with everything that's different.
Nicci-chan: That actually sounds pretty cool; I really loved both seasons of the anime. Are you saying that you would DM it?
Yeah, I would DM and make Horo into a druidess of sorts. Really the only class in D&D that can apply to her at all. Also limits me to have it be at level 6 starting, that way she can turn into a large wolf and scare some peasants senseless.
Naturally when you do stumble into her, she won't have any magical items, being stuck in the land for a few centuries and everything. Druids don't need magical weapons or armor anyway, so no big loss.
Speaking of magical items. There will be those in this game, but since this is a medium-low magic world, all of the magical items are crafted by the church, and via their monopoly they charge 1.5 times more then what the base prices are.
The idea is yes you can have magical stuff, but only after the permits and praying and dealing with greedy priests and under the table bribing to get the paperwork done and MORE praying.
So level 6 starting.
5d6 epic rolls. I like my players to be slightly OP so I don't feel bad about throwing mean baddies at them.
16,000 starting gold.
3 Players only. Any more and it bogs down the game.