Shahab323is:this makes me want to get something like maxqdata so we can compare numbers, maybe help me see where I need to improve
^^This. If you just look at your own runs, it is helpful. If you can compare with someone else (best case scenario in the same car, or similar car), then it becomes an exponentially better tool.
The GPS data is tremendously helpful to both me and Brian to see what elements of a course we are better than each other....and then coach each other to "clean up" each others trouble areas.
I really think it helped me become a better driver by seeing exactly where I was getting my arse kicked. What may have taken years in the past to figure out, can be at your fingertips instantly. It's a brilliant device. 
Will Lahee -- Indy Region
Section 8 Racing
Knowledge is realizing that the street is one-way, wisdom is looking both directions anyway