The SP-100 and other small-sensor cameras don't deliver the photo quality of a dSLR with a larger sensor. That said, as long as you're not pixel peeping or don't typically enlarge and heavily crop your photos, this Olympus turns out very good results, especially from ISO 125 through ISO 400.
That means as long as you're shooting outside in daylight or inside with a lot of light you'll get nice-looking photos good for larger prints and sharing online. At ISO 400, subjects start to look a little soft and could use some post-shoot sharpening. Although noise levels are decent, the softness gets a bit worse as you increase sensitivity until you end up with no fine details and colors desaturate. While ISO 1600 and 3200 might be usable at small sizes, I would avoid using ISO 6400 altogether.