Running a campaign there now. I'll skip the Faerun bashing and give you what I hope you need to know.
1.) Gritty nastiness. The Gods just recently destroyed the Titans, the entire continent's ecology is screwed up with foul, monster-spewing locations, big chunks of land are inhospitable and teeming with ruins. Adventuring makes sense. In a lot of other settings, I'm always thinking "There's a city RIGHT OVER THERE, why haven't they cleaned out thses tombs...?"
Although the gods are not in-game, their recent appearance and well-designed pantheon revitalize clerics and paladins - ordinarily not easy characters to push past stereotype. These religions have personalities and agendas.
Their version of the Harpers are the Vigil. Not travelling adventuring poets. Think the Spartans. Brutally trained, devoted, relentless, and not above dying unpleasantly en masse tp protect the innocents.
2.) Political fun. The Southern section of the continents is controlled by Calastia, a kingdom of nations of not-necessarily-evil-but-still-very-bad guys. They're looking hungrily towards expansion. The Elves don't have a shining kingdom - they live in one of the last big forests and gaze out at the human insanity warily. The dwarven capitol of Bork Torm has been under siege for decades. Vesh to the North is a nascent republic, and the western coast is a hodgepodge of good guys and bad guys, with lots of "contested ground". Kingdoms have enemies who are specific enough to build adventures around, but whose structures -- even in the supplements -- are fluid enough to tweak for your own game.
Add to that the world's the right size for cross-country travel without the need for teleport spells.
3.) low-to-mid level magic. Even though there are the same spells, the feel of adventuring is constant danger and bad-asses trying to kill each other with sharpened pieces of metal, not huge spell duels. There's one high-magic race, but they got temselves wiped out a while ago, and nobody's all that happy at the thought of them coming back ...
4.) The overall tone. Besides the Gazeteer, each major location and faction is getting a splatbook, and each is detailed enough to run a campaign from that location alone. That, and each has a very, very distinct feel.
Hollowfaust - city of the surprisingly un-evil necromancers. Mithril, the shining outpost to the North with a very seamy underbelly. The Calastian sourcebook almost convinced me to run a campaign of good guys in the service of a bad Empire. Each book contains prestige classes and multiple adventure hooks.
In summary, Scarred Lands is the perfect blend of enough details to save you time and inspire you as a DM and flexible enough to drop entire mini-campaigns in the blank spots.
And I recommend the Monsternomicon heartily. The creatures are well-designed and the art's gorgeous. The tone of those monsters fits perfectly with the Scarred Lands.
Have fun.