Not as bad as I originally thought after watching the game reveal - visibility atleast. I remember one game, we chose a draw bridge as a defense, and I couldn't see a good quarter of the field. The nice thing was, we planned for this, with a really long controller wire, and more often than not I was walking around the full width of our driver station.
We used a camera only for going back through the drawbridge.
My operator would also be watching the robot, and let me know if I don't notice something. Also, our robot, in the configuration it would be in throughout most of the match, can be seen over the sally port, which was actually designed in.
One of the biggest inconveniences were the boulders, driving around them, having them in awkward positions, trying not to incur tech fouls accidentally taking a boulder over during a crossing.
Hard to play defense, you don't really know when bumpers are over the vertical projection of the outer works if they are anywhere near it, or in the neutral zone.
The one use for a spy I saw personally - not for us, but for say an outerworks shooter, was for the spy to give a signal (simple as a thumbs up) when the bumpers are in the outerworks - hence the robot is protected by defense. This did not apply to our strategy.
Edit: Oh, and the batter dividers were always fun
