I just bought one of these because I lost my vag-com cable and I needed to identify a problem with my Jetta. I'm sure the cable is somewhere. Anyway, it found the codes that my Jetta was throwing and worked just like it said it would. For the price, I think it's fine. It's not awesome, but it worked.
I like that it's powered off the odb2 port. That way, a crappy battery isn't going to leak and destroy $18.
One thing to know - the manual is actually between two pieces of cardboard inside the clam shell. I didn't realize that and cut the manual in half. The unit's pretty self-explanatory so no big loss there but if you want the manual intact, don't cut through the cardboard inserts.
