Atmospheric conditions and lighting will play a huge role in your effective distance with any optic.
I owned / used this exact spotter for 3 seasons. In favorable conditions, I have been able to evaluate mule deer well over a mile away. By evaluate, I mean being able to determine if he is a good buck or a smaller buck. If the sun is right, I have been able to determine points and other details as well. In order to fully utilize the maximum magnification, you will need to have nearly perfect conditions. Otherwise, the image may get grainy and dim. In many reviews, you will read that this is a very good spotting scope for the price, and in my opinion this is true. Only reason I sold mine was to buy a Swaro spotter.