The biggest advantage of Panasonic GF (as well as Olympus EP series and E series) is the balance between portability and image quality. Its portability is beyond the reach of SLR users, so SLR users can only emphasize their own image quality, but the appearance of Fuji X-Pro 1 proves that excellent image quality is not the patent of SLR, and I have contacted many SLR users who are actually eager for a portable camera with excellent image quality, such as Leica M9 (but it is too expensive).
Compared with other brands, GF series has many lens groups (a little more bull's head), wide market positioning (female users GF5 positioning, professional users GX positioning), fine workmanship and comprehensive functions (both).
GF with biscuit mirror can be said to be the best combination. (Micro single-switch SLR lens, sacrificing portability, is actually putting the cart before the horse)