I bought AP during the holiday sale (it was 10).
I really dig the game. It plays very much like a single-hero focused HOMM. Your hero has a more in-depth customization system with a "WoW-esque" talent system. Everytime you level up, you get a certain number of 3 types of Runes, depending on your class, and then you spend the runes to buy abilities in your talent trees.
In AP, (not Legend), you also get a pet dragon that grows up and levels with you that you can use during fights. They can do stuff like search for treasure, smash bad guys, drop walls to manipulate the terrain, drop eggs that make one-shot units, tons of cool stuff.
The only negative is the really shitty story. It's badly written and generic.
Like, the very first scene is your kingdom being attacked by demons. A wizard has this hourglass that freezes time for everyone except the one who breaks it and he's planning to freeze time and teleport to another dimension to find allies. You come in, say I'M THE PRINCESS IM GONNA DO IT and smash it yourself. It's dumb.