Well- I'm still delving into it (and I'm on my way out the door), but things that have caught my eye include:
The setting is strong on flavor. Its generally well though out with a good eye towards historical detail, and how those details should change for purposes of the game setting.
Northern Crown is set in a 17th Century America in which magic really works. The Indian Nations are still strong, the Uropans have not progressed as far inland as they did in the RW. As I mentioned before, while not designed simultaneously, NC integrates well with Nyambe, and in fact, certain class and culture combinations cannot be played without Nyambe.
Similar to Nyambe, PCs are generally limited to playing humans, with differences in CULTURE creating differences in starting stats, feats, etc. There are about 15 different cultures depicted- several Uropans (Espaniards, Albians, Kelt, etc.), First Ones (Mowhawk, Ojibwa, etc.), Cimmerons (Nyamban-Americans

), Free-thinkers, Buccaneers, and so forth. Characters with the Two Cultures feat can qualify for benefits from both cultures the PC is a member of, but can only take the free feats of one of them.
While the designer points out the traditional roles for women in each culture, he also points out that PC females are free to escape those boundaries.
They eliminate Barbarians, Fighters, Monks, Rangers and Rogues (this one confuses me most, see initial post). New core classes include Agents (spies), Rakes (dandy duelers), Raiders (combo Ranger Barbarians), Soldiers (trained military), Witches, and Natural Philosophers. The NPs are my fave so far- these are the inventors and artificers of the setting. Think of them as analagous to specialist (techno) mages who use non-magical inventions to duplicate magical effects. They can produce Antimagic, Life & Death, Mentalist, Physical and other effects from a limited "spell" list, have Metascience feats, etc. These are the guys and gals who create automatons, flying machines and energy weapons...
PrCls include (not an exhaustive list here) Falstaffs, Sea-Captains, Officers, and Tall Tale Legends*. That last one gradually turns your PC into your own version of American folk heroes like Paul Bunyan, Johnny Caw, John Henry, and so forth- complete with Size change and oversized animal companion. Falstaffs are named for the character they are modeled after, and are a little like Drunken Masters.
* The one problem with this PrCl is that it is too slavish to a few Tall Tales. Hopefully, future expansions of the game will also expand this PrCl to encompass other legends.
There are 3 Psionic Feats that have a slightly different structure than the XPH. You can have the Evil Eye, be a Firebug, or have Second Sight. They aren't classes, they just give you powers and PSPs based on levels. In a sense, they are most like the 1Ed & 2Ed Psionic Wild Talents using 3.5Ed mechanics.
One thing I'm not clear on at this pont is whether your PC can only take classes listed under his culture or not. I suspect not-but I haven't had a chance to sus that out completely.
I'll post more later when I'm back!