EFI Live is the single geatest thing that has ever happened to GM V8 gas and diesel vehicles.
You can have total control over every aspect of the engine. If there is something you don't like, you can change it. If you need more power down low and not that much up high, you can make it happen. If you have an LLY or LBZ and tow, you can change the boost to bring the EGT's down. You can improve mileage and power at the same time. If you like smoke, you can build a smoke tune that will cover a 4 lane highway, or you can build a 450 hp tune that hardly smokes at all.
Basically, EFI Live is the ultimate tuners dream. My next car is for sure going to have an LSx engine so I can use EFI to tune it.