It is very easy to use, but there is a lot of trial and error when it comes to tuning. You have to add fuel and see how she runs and if it's too rich, then take it away and so on. But the thing is, you have to to this through all throttle positions and rpms, so it does take time, and if you don't have someone else to drive the car while you do it, then it's even harder cause you have to do it all while you are driving (like I am doing).
As for if it's doing the job, hell yeah!! You can tell immediatly when you add fuel or take it away. I have mine still rich and can really tell it's using a lot of gas becasue I have to fill up a lot more than before, but I'm still tuning, so hopefully later it won't use as much. In regards to timing, I don't know how to tell if it actually is retarding timing. I have a -4 degree retard at full throttle and it degresses to -1 just over half throttle. I am running 8PSI right now and have yet to hear detonation, but that could also be because of me running so rich. This unit DEFINATLY is a must have.
BTW My tuning is taking so long because I have the 80mm mass air on it. When I had the stock unit on, I did not have to tell the stock injectors when to fire, so there was a lot less tuning, all I had to do was to add fuel via the extra injectors and the timing and that was it. So if you will be staying with the stock unit, the tuning should be a snap! Hope this helps.