No device is picture perfect and neither is the paint zoom perfect. It does suffer from issues that are inherent in its design and cannot be circumnavigated by any means. What a person can do is to simply cover up these issues with whatever is available to them. For starters, it does have the problem of painting extra surfaces because of paint that escapes from the extreme nozzle openings. This means that you might tend to paint over areas that you never intended to. Hence, it is best to use tapes or newspaper clippings to cover up those areas.
Furthermore, it also does not fit too much paint in a single go but that is a design element central to its functioning. If it fit too much paint into the container then its weight would increase making it hard for housewives and general users to make use of. This device is meant to be a good replacement for brushes and rollers not to be used in industrial applications.