how good is it and  what will it do to my truck it is a dodge ram 1500 v8 5.7 liter motor with a hemi  

hehe...what doesn't it do, lol... the typical thing it has is a choice of 3 tunes, 87 performance, towing performance, 91 performance.  you can raise the speed limiter from stock (~105) all the way up to 140mph, you can adjust 1-2 an 2-3 gear shift points, as well as rev limiter.  you can also adjust for tire diameter. it also reads and clears check engine warnings. that's pretty much the std stuff, the cool stuff for me is the logging an monitoring.  you can get e.t. times from 60ft all the way to a 1/4 mile (just like at the track), you can also monitor fuel trims (important when you start to custom tune), engine temp, air temp, knock retard and various other info on the fly...i literally have mine connected everytime i drive just to monitor fuel trims an temps...

I hope this helps...fred