On my ScanGauge E I have a tab for Voltage and Open/Closed Loop, but I don't use it often. Both LOD and LP can be useful for reminding you to get your foot out of it.
Mostly I watch Coolant Temp, Average MPG, and Instantaneous MPG. (I would watch intake temperature as well if my '96 Outback provided it.)
More broadly, I bought my SG more or less as a toy, but it has paid for itself just in scanning codes on cars among my friends and family. I don't exaggerate when I say I love this thing.