Sambo, I use HPTuners software which is what most tuners in the country use now. It now also supports all the new 6 litre engines (though I haven't bought any of the 6 litre licences and probably won't).
I was using the scanner just to check that everything was running ok, (I just flashed my MAFless Ute program into it) and to manually turn on the fan if I had to. The fuel trims were very positive but I reckon that's just because the engine is still new and tight, and the O2 sensor signal being slightly diluted by fresh air. I will tweak the fuel trims after I have the full sidepipes on I guess. Everything else was doing the right thing so I'm pretty happy.
Using the scanner at the track is a great idea! I log every run at the dragstrip and tweak it slightly if I have to. That's how I get an unopened LS1 Ute to do 11 second quarters...
The advantage of logging at the circuit, (apart from all the engine related information) is the TPS, RPM and speed displays. These will show your weaknesses, (perhaps?) which you may use to improve your performance at that particular track....