I like using the tach. I learned to tune by ear and then when I bought a tach I found that I had been running more rich than I really needed to. I can put the nose up with low fuel and find my worst case scenario peak for any plane, then check it again full and level to see how rich I need to be. It also tells me how well my low end is tuned and how steady the engine is running in general. It takes lots of the guesswork out of setting the needles and makes turning the low end quick and easy. I can and have done without it, but anything that makes the task easier or faster I'm all for it.