ORIGINAL: S.R.G.
I understand the eyes, ear, sight thing, but want the temperature gauge to double check everything, know temperature of engine in relation to environment, different fuels, and different setups.
It's not bad to have a temp sensor, I still have that habit of temping my engine. When you temp your engine, dont let it alarm you if you see high temps.
Totally ignore the temp recommendations of your engine manual, they are stupid cold. That is page you can rip out of your manual, useless BS from the manufacturer.
For my small blocks, the manuals tend to say around 200-240 degrees F, but I have temped my engine at 270 degrees F, and all the other cue tell me it is running just right, so I keep on running it at its current needle settings.
For big blocks, totally ignore what teh manual says. 250degrees F is stupid cold, these engines will easily break 275 degrees F and push even 300 on a good tune, especially on a warm day.