For being one of Nikon's highest end Coolpix cameras, the S8000's photo quality is pretty average. Photos taken at ISO 400 and below are good; they have low noise and decent fine detail, so light cropping and enlarging are possible, resulting in good prints up to 8x10 inches. With no cropping, you can probably go slightly larger without seeing soft, smeary details. Above ISO 400, images look more like watercolor paintings than photos. At ISO 800 they're still usable for small prints and Web use, but go any higher and you end up with soft, smeary subjects and blotches of yellow and blue color noise.
In Auto mode, you have a choice of two fixed-range auto settings for ISO: ISO 100-400 and 100-800. When possible, use the former. If you're using the full 10x zoom range, you're indoors, or in low-light conditions, switch to the latter.