For me Karlin is the place for longer stays in Prague. Fab neighbourhood cafes, tram to center (walking distance without transport if so inclined), groceries close, parks to walk and riverside for run, too. Flat was what I needed: privacy, safe entrance, washing machine, basic kitchen, always working shower, large windows and high ceilings, and nice host who told me how to fix internet which is not the fastest if your work depends on it (allegedly walls too thick to have good signal in every part of place). Overall, good experience.