It's large enough, I'd say. The campaign setting book details two continents roughly the size of Europe.
All the regular D&D races. No major new races, though there is stuff like sentient flying apes in the jungles of the Mwangi Expanse, and so forth.
If you play 3.5, classes aren't different, though there are some new optional class abilities for each of the PHB base classes in the campaign setting book. There's even one that gives fighter decent skill points and class skills. There are five prestige classes in the campaign setting book, a couple of more (mostly religion-based) in the adventure path books. The ones in the setting book are Harrower, a gypsy fortune-teller with a special deck of cards (That Paizo actually sells. I think it won an ENnie.); Low Templar, a self-serving, opportunistic crusader who must ultimately choose between good and evil; Pathfinder Chronicler, a bard prestige class for members of the Pathfinder Society; Red Mantis Assassin, which is pretty much what the name says; and Shackles Pirate, a reaver of the seas who gains supernatural powers from his connection to the Eye of Abendego, a permanent maelstrom.
I'd call Golarion the ultimate kitchen sink setting. There's a place for everything in there, though in some of the more out-there cases it's a really small place that you can easily ignore. There are firearms in there, in a small and remote duchy somewhere in Garund, and there's a barbarian land where a humongous spaceship has crashed, granting the primitive locals strange materials and equipment. There's the Land of the Linnorm Kings, for the Viking myths, and next to it is Irrisen, a country founded by Baba Yaga, for the Slavic ones. I would not call Golarion "vanilla". I'd say they bumped off the ice cream salesman and ran off with the whole cart.
Geographically, think of Europe and Northern Africa and you won't be far off. The similarity is striking - you've got Avistan, with the European-influenced cultures (and a couple of places really out there) in the north, and then you've got Garund, with the Egypt-analogue, the big desert and the jungles of the Mwangi Expanse down south. In between, there's the Inner Sea.
Politically, we've got all kinds of interesting things. There's a theocracy of Asmodeus, a fledgling democracy, a lot of aristocracies with different levels of decadence and so forth. Qadira, one of the major players of the Inner Sea region, is actually just the westernmost province of a great eastern empire.
The planes are a bit different, in that there are less of them and the setting doesn't use the Great Ring, but the inspiration is clearly there. I think I'll adapt the Great Ring for Golarion when I start running it.
There are no notable exclusions, I think. Golarion is notably inclusive.
What caught my eye about Golarion is how they've nearly tailor-made a place for each of the classic D&D adventures. There's your Egyptian desert for the Desert of Desolation series, your yellow-sailed Okeno slave ships for the Slavers series, the giants of Varisia living right atop the drow for some GDQ adaptation, a land of gothic horror for I6 Ravenloft, and so forth.
Also, there are troll diviners who cut open their own stomachs and divine from the entrails. That's in Classic Monsters Revisited and one of the adventure path modules, actually, but damn, it's awesome.
I don't have Guide to Darkmoon Vale yet, but I liked Guide to Korvosa.
