I have used the R800 for printing disc's. The output is excellant, you wont be disappointed. You need to print at the heavy ink setting. Cant remember what it was called but you will see in the printer dialog box what it is called.
The software that comes with it is totally lame.
As others have said you can setup a template in photoshop and import it into the epson software that came with it.
i didn't have photoshop , i had freehand 11, a vector art program. You can download a 30 trial of fully functional freehand 11 to try out. I have a template setup that is a freehand file. You just open the file in freehand and the template outlines are setup. You just put yor artwork inside the template lines and then print the file out to the R800 through th print command within freehand. this totally bypasses the epson software all together.
The tough bit was working out how to get my diagram in freehand to line up with the DVD on the R800 as you are outside the epson program doing it this way. I managed in the end and got it perfect. As i say the outlines are setup and locked so you cant move them . The outlines are setup as non printing on a locked layer. This means you just put your art work within the lines and it prints on yor dvd.
let me know if you want a copy of my freehand templates. then again you may decide to go the Photoshop route in which case my files wont help you ...of course.