All of the available disc printing software seems pretty awful, especially if you are used to vector graphics software.
I tried every one I could find after getting my Canon MP970. Canon's own software seemed the best of a bad bunch, but the alignment options were just too slow and limiting. My requirements were modest, just a few lines of text and single small image, but it was virtually impossible to produce labels with a consistent style & layout.
So I created my own template from scratch to print directly from an old copy of Corel Draw. It should be possible to do the same using Inkscape, Adobe Illustrator, Xara etc.
It was surprisingly easy to do. The first print preview was 0.2mm out, but with that corrected the first disc was spot on. Apart from a single disc using Canon's software, every disc I have ever printed was done from Corel Draw (probably in excess of 500). The only problems were due to operator error.
Using this method I can create new labels very quickly to a consistent style using the guidelines saved in a template. Or when necessary I can easily modify the design, but keep a similar style. And you have access to all the effects, such as feathering, supported by the software.
I was going to post my template here, but nobody seemed interested. If anyone is still using a Canon Tray-F printer and would like a copy, let me know.