Day one, with a TB47 and a TB48 battery, I flew 112k feet total (21 miles), on 5 flights. My max distance from base was about 6000', at 350' altitude. I was EASILY able to see the aircraft at that distance, discern its orientation, and clear the airspace (at dusk). It was actually quite remarkable -- the Phantom 2 becomes invisible much sooner than that. I think it has to do with the positioning of the LED's on the Inspire 1 -- they are oriented outward, instead of downward as in the P2. Very easy to see it and tell red vs. green.
I fly mostly ATTI, only using GPS when I want it to hold its position for some reason or other, or activate RTH.