For intervals, I look at time and 3second power.
For long fun rides I look at total distance and time of day.
For steady state efforts (time trial, ftp test, 20min interval) I watch HR and 3second power.
For long climbs, I look at elevation because I know the altitude of various peaks. It helps me stay motivated as well as pace.

So, only one or two numbers are important at any given time.