I touring/audax rides I normally have the time of day, trip odometer, heart-rate and elevation displayed on my eTrex, plus turn instructions when it's navigating. My conventional cycle computer displays current speed, cadence and temperature alongside.
For racing, I have elapsed time and average speed in large friendly letters, plus some other stuff that I only look at if I'm not trying hard enough. My cycle computer on there does current speed, heart-rate and cadence.