I have used a Sig 2000 for several years and have never babied it. It has been spot on. The only gripe that I have had, is the large target circle. My buddy just got one on BF from Cabelas (for just over 200 bucks) and they made the circle a bit smaller in the new ones.
The farthest that I have ranged critters, was a herd of antelope on a snowy background at 780. That is well beyond what I need, anyway.