I've only owned a tac for one season but I find it best for finding highest RPM at max throttle so I can then back off two or three clicks. Knowing the leanest mix is nice but knowing I'm not destroying my cylinder sleeve and piston is nicer.

As far as idle, I can't much fault Cyclic Hardover's description. I might say it's the lowest speed that allows the engine to continually run.

The 9C radio (others too, I'm sure) has a great feature in the throttle end-points that allows a throttle cut switch AND a switch that flips between very low idle (landings, spins) and not quite so low an idle (taxi, downwind legs). Nothing worse than taxing out, yelling "TAKING OFF" and then having it die before you throttle up. The "Idle-Down"