I haven't had time to really dive into them yet, but I really like the sorcerer bloodlines. That feature adds such a great dimension to the class that it creates all type of possibilities for PCs and NPCs.
I didn't think I'd like it, but I'm also liking the changes to the spells that make them less save or die and more hit point damage-based (like implosion).
I like some little changes that change minor rules that I used to house-rule out anyway, such as the "death from massive damage" rule. First, they officially made it optional, and second they made it "half hit points, minimum 50". So if you have 500 hit points, you don't worry about a single attack doing 50 points of damage causing an issue - it would have to be a 250-hp incident.
I like their "most important rule" which I won't spoil here since it's supposed to be the topic of tomorrow's Paizo preview blog. (Nothing earth-shattering, but it does provide insight - I hope - in to the gaming style at Paizo.)