Beware of "TMI" with the Garmin display.
Sure, you can display 8 fields, but can you safely *read* 8 fields while you're riding down the road?
I used to have a bunch of fields open, but found I spent too much time looking at the display and not enough time looking at the road! I've whittled it down to - I think - 5: Speed, distance, cadence, HR, and Time of Day. It's still too much, really, but I'm a junkie and can't give up any more! I keep extra displays of all those cool things I'd LIKE to know on the 2nd computer display: average speed; ride time; grade; and something else I forget. I toggle b't the 2 when I can safely do so or at stops.