I don't know about anybody else, but I find that, generally, it's hard for me to see other GA traffic during the daytime until they are within 2 miles, even if I know where to look for them. If the G1000 TIS or ATC calls out traffic 5 miles away, or 3 miles away, if it's your typical sized GA plane (Piper, Cessna, Mooney, Beech, etc.), it's hard to spot them any further out than that.