My friend has a tandem and he and his wife have two 800s that they use. Seems like a bit of over kill, but to each their own.

Just rode a late afternoon hill ride yesterday in Philadelphia, we managed to beat the thunderstorms. On the ride back to the Art Museum it was getting nasty dark with a few lightning strikes flashing behind us. I had on script sunglasses and it was after 6:30, yet I had no problem seeing and reading the screen. Many of the data fields use much larger fonts and it will completely readable, add to that I don't have the best eyesight going.

The navigation worked perfectly. Our ride was one that we mapped out on ridewithgps and we had yet to have ever rode the course before. We had no issues with the navigation. The 800 is a clear winner for me.