That's just it - I never used a sight until I switched to a compound, which was last year. But so far I've only used the compound at a range, not out hunting. The range slopes, but I didn't realize how significant that slope was at merely the 20m mark. I've been shooting at 30m and assumed at some level that the indoor range at 18m would simply mean going back to the top pin with minor visual adjustment. Not so.
But then, the indoor range is on the 3rd floor in a very old building and I don't know how level the floor really is. I think I'll check that out next time.
@Jeff - His politics aside, you should watch Nuge hunt. Much respect to anyone who can take a running pronghorn with a bow from 100 yards without sights.