Much better than with the 75-300 Canon lens. With the lens stopped down and on a tripod with a fast shutter speed the quality could be good enough, depending on what 'good enough' means to you. Part of the problem is that you have an f8 560mm lens, so getting a fast enough shutter speed to avoid vibration blur is a problem. Haven't tried this enough to really know. The lens is small enough when zoomed in to 200mm to fit in a camera bag and carried on a hike.
Optical quality seems fairly good, as does the mechanical quality.
Whether this lens is for you depends on how much you are willing to spend, and what optical quality is good enough for you. The focal length and the maximum aperture pretty much require it. These are my first impressions, your mileage may vary. And I apologize that this was so long.