While looking at the list of bugs ~suv sent, I realized how much space there is in the Symmetry tab, much bigger than is needed for a simple preview of symmetry types. So, since the Tiled Clones interface is so confusing, why not simply add instructions into them? After all, I've noticed that they don't have to be long, they just have to be easily found by users.
I've made a wiki page gathering everything so far (though we may need a new list of symmetry previews since Thorsten is experimenting with the preview styles)
http://wiki.inkscape.org/wiki/index.php/Tiled-Clones
As you can see, Simple translations now has tips for rotation, for example. This way, I think there's no need to have something separate for radial transformations, since users can just follow instructions. For anything more complicated, they can look up details.
They will also be useful for P3 and P6 type transformations. I still haven't managed to get them working myself, so if there needs to be value input into the Shift or Rotation tabs, now's the time to say what is needed? Thanks! :)
Feel free to mess with the wiki page.