Town and Spear Militia are gone. Now Spearmen are also recruitable at cities (and cities can recruit better units, though not as fast as castles). A lot of name changing has been going on. Now Spearmen are Levy Spearmen, Mounted Sergeants and all those light cavalry are Mounted Men-at-arms, Armoured Spearmen are Men-at-arms, General's Bodyguards = Sworn Swords, and more changes. Oh, the generic Armoured Swordsmen are mostly gone. Real un-Westerosi unit if you ask me. They are however present as Marcher Swordsmen, only available in Stonehelm and Blackhaven.
AOR system is the following:
Regular southron factions can recruit Levy Spearmen, Archers and Crossbowmen in all regions that are not Dornish, Northern, or Iron Islands. Exceptions are Arryn and Lannister, whose spearmen are unique and can only be recruited at starting regions. More advanced units, such as Knights and Men-at-arms can only be recruited at the faction's starting regions (AOR), to simulate the fact that minor houses which provide most of the armed men would only fight for their Lords Paramount.
Joff, Renly and Stannis all share an enormous AOR, consisting of the Crownlands, Stormlands, and Dragonstone and Driftmark. Since they are all Baratheons (well, Joff is a special case

), and all are vying for the throne, allegiances become rather murky. So Joff, Renly and Stannis can recruit all their pro units in the other Baratheons' regions as well as their own.
Martell only recruits in their own regions. However, they don't have to rely on weak levies, so they are stronger on that respect. Plus they have more varied (and thus more numerous) cavalry.
Stark recruits in the North.
Ironborn recruit on the Islands
and Raiders can be recruited at any region with a port.
Moat Cailin recruits NO units. Harrenhal can only recruit basic levies and sellswords (see below).
Sellsword units are now more widespread, recruitable at large and huge cities, and fortresses and citadels. Still, Stannis can recruit in higher ammount due to having the Sellsword Guild at Dragonstone