I have been thinking about getting one just for the additional items that Peter mentioned. Knowing what RPM the engine is running at and what kind of load it is under are things that I am interested in. I have NAV, so I don't really need it for the FE info, as my display sits on the consumption screen about 90% of the time (the othe 10% is a mix of maps when finding a new place or audio settings when flipping thru stations).

I don't think it can be used to change any settings in the computer. I believe it is a read only device with the simple ability to clear codes if desired.