As is typical of Panasonic's cameras, the built-in, default noise reduction delivers subpar results. Here, if you look at the text, you can see the bump in color NR between ISO 400 and 800 with the concomitant loss of sharpness. However, even as low as ISO 200 the color noise starts to impact the text. Stricly from a noise perspective, I wouldn't shoot JPEGs above ISO 100 in anything but bright sunlight.
Noise, ISO 100, raw vs. JPEG
Even at ISO 100 there's some unwanted noise on flat neutrals--look at the gray card--using the in-camera noise reduction. In part, it looks like it's exacerbated by excessive sharpening. A quick-and-dirty pass on the raw version produces much better results.
Noise, ISO 1600, raw vs. JPEG
If you deal with raw files, you can get relatively usable results up to ISO 1600.
Even at ISO 100, JPEGs can have these horrible crunchy artifacts in non-close-ups. I think it's partly due to oversharpening, which can be adjusted in-camera. However, there's no similar problem for macro or zoomed-in shots, so there's no way to globally set the appropriate level of sharpening to cover both situations.