The GF5 shows some improvement in its noise profile and JPEG processing over the GF3, especially at low ISO sensitivities. It seems to primarily be attributable to a less noisy image coming off the sensor, an expected advancement from one generation to the next. While there's a noticeable jump in noise-reduction artifacts between ISO 400 and ISO 800 in the JPEGs -- most notably smearing -- Panasonic has improved the processing of high-contrast areas. For instance, the gorilla's fur and the rose become quite smeary by ISO 800, but the text doesn't suffer too much. The lens you use makes a big difference as well: while I wouldn't suggest shooting JPEGs past ISO 400 with the 14-42mm PZ kit lens (used for shooting these test samples), for a good prime lens I think I'd bump that to ISO 800.
Though it's a little soft and you can see some artifacts (look at the flat surface of the building in the upper right corner and the edges of the illuminated elements of the clock face), the GF5 can resolve detail pretty well with the right lens.
The ability to tilt the flash back to bounce the light (top) makes a huge difference in the quality of some flash shots. It doesn't have enough power to illuminate distance shots, such as group photos, but it's great for close-ups.
Panasonic lets you dial in the intensity of most of the filters as well as adjust some contextual options. Overall it has the typical set of filters (I don't have examples of the miniature or one-point-color filters).