It sort of depends on what kind of sharpening you need done. If the knife is completely dull, it's going to be difficult to properly remove enough metal to raise burrs with the medium and fine grit. The ceramic stones are excellent for touch-ups and maintenance, but you'll need the knife's edge to already have a reasonably sharp edge and geometry for the ceramic to work, otherwise you might just be spending a long time trying to remove material.
You'll most likely want to use the 30 degree setting most of the time, as the acute 20 degree angle would not be touching the actual edge of most production knives.
Diamond rods are much more coarse and better at removing metal, but I personally prefer to use a simple benchstone for any heavy profiling and metal removal.
The ultra fine rods are good to use if you are aiming for a highly polished edge. Though it will probably be better to buy a strop if you want to really finish off any edge from the fine ceramic. The ultra fine just help to polish out the scratches and bridge the gap between the fine stone and a very fine abrasive from stropping.