The problem with most trackballs is that their sensors are way too low res to do any real drawing. They're great for 3d apps, but not much for photoshop. My gaming trackball hack isn't that bad since I can up the resolution to over 4k+, this slows the movement way down however and while I can get straight lines with it, it's painful to get a real stroke. Tablets are really the only good, practical, and efficient way to use photoshop, plus you really need pressure sensitivity which only wacom tablets do well, otherwise you might as well just use mspaint.