From what I've read, it's not a really useful feature for the VTX. (according to Johnnycheese on the vtxoa board) But Jim Sabin says he usually plays with it a little.
What Jim told me is that it's not something you can 'tune' on the dyno, it's a riding style thing. I didn't use it on mine but I may experiment with it sometime. I think Jim said to maybe start with 15% more fuel for 15 engine revolutions and 80% sensitivity and then play with it from there. When I finally get to go to the track by my house I may fiddle with it then and see what my reaction times do.
But if you don't have easy access to hook it up to a computer, I would suggest you just leave the feature off.