I read some of the negative reviews and decided to buy this anyway, and I'm glad I did. It takes some getting used to because there are so many options for reading ECMs on a car. After a little learning curve, it becomes very easy. I must've saved at least $1000 diagnosing and repairing the car myself. The device does not come with batteries (four AA), but it comes with a cable to attach to the OBD plug in the car and a very nice protective case, and also has a pretty thick, detailed user manual.