I am developing a small Android game. Before I started using AndEngine, I used the Canvas object and draw everything on it. For testing if two bitmaps collides with each other I checked if their bounding boxes overlap. In case of this, I checked if the overlapping rectangle of both bitmaps got one none transparent pixel in common. This method worked perfektly and I was able to detect pixel perfect collisions.
Because of some performance issues I started using AndEngine. Collision detection works quiet good but collision tests for two sprites definitly dosent work pixel perfect. The collision tests is "just" a bounding box test.