I think I may have gone a bit too wide in those two examples ... which gives you skinny ... :)
Yeah, if you make it wide enough, you can almost see everything on the map at once... it's trippy. Eventually, you just see a set of arms holding an incomplete gun model floating in space.
I don't know any technical terms that apply to perspective, but I would imagine that if focal point of the FOV were larger, you could cram more into the view without distorting the image as much. I forget what setting I play on, but I think it's about 103 degrees at 1280x768. It makes up for the loss of vertical FOV and provides the minimal distortion.
Having played Halo for a LONG time - even on Xbox - it took a lot of getting used to the "enhanced" FOV. You appear to get closer to objects faster - sometimes you're closer to grenades than you expect as well...