I own one, mainly for fuel economy purposes and it works great. It is also possible to program other information to allow real-time monitoring of these. For example, I programmed a trip fuel economy to supplement the instant fuel economy information on the main screen. I also used it to clear a code after coming back from a trip, with my car not moving in at least 3 weeks. I got the code (for low voltage of something) and cleared it, and it didn't come back, no problem with the car.
I recommend buying it online for those interested. Much less of a bother than hunting for a store that has it.