Used it in my theses' app, a great framework for the early time it was created. Easy to begin using. Various setup examples to play with. Location, gyroscope and velocimeter work well, although step counting and world walking do not seem to work.
Used it in Native Android for my theses' app. Great marker and image recognition. Although it lacks the 3D target recognition, only works with flat surfaces on cubes and parallelepiped volumes.