I have one on my gixxer 750 track bike.
The good thing about them is you can only add fuel, so you can't kill your engine by making it too lean.
Get on a good quiet road, with a screwdriver and take runs. write down your adjustments. When you go too far you'll feel it, so back it off until you're happy.
Fueling issues and alterations are very easy really. Everyone knows the fueling is wrong when they feel it. People think they don't know if it's right or wrong, but that's usually becasue it's right. If it's wrong, they'll feel a dead spot etc.
Each screw does something different, so you have your low end, mid range and top end etc. It's trial and error really, but you'll know if it's wrong. I've not had a before and after dyno as it was on when i got the bike, but it makes the bike extremely smooth and consistent when applying the power, like no other bike i'veridden. very very smooth power output.