I give this app 5 stars on two levels. First, the app is pretty amazing. It takes a little time to get familiar with all of it, but I have found that after I got all my graphs set up the way I wanted, it was really helpful.. You don't have to be a professional race engineer to benefit from this. When I'm practicing for a race and I rip off a lap that's .5s faster than usual it's great to be able to look the data and figure out why so I can reproduce it.
On the second level, the developer Iko Rein is amazing. I had kind of a weird issue with how my ACC was sending the broadcast data to the app and he helped me work through it. He went well above and beyond to help me. This is an app worth supporting with a paid license if you can afford it.