Personally, my car is only race driven, therefore thoses gauges are quite necessary. I have three gauges, oil pressure, water temperature and a tacho with shifter. They are all definatly necessitys, I would be blind without them! Gauges such as oil pressure are very important when you are thrashing your car around 8500rpm like mine. You needd to know before a engine seizer occurs for example by dropping oil pressure.
However I agree, on your average road car that's stock standard, the factory gauges will definatly do the trick
I agree seeing gauges like exhaust temperature and intake vacume on a standard car is a bit out of it
, but yeah, thats my opinion