The LabelTag software actually pops up after you hit the BURN button in Nero. It's exactly how Dee explains it. It uses whatever space is left over on the disc. The label looks super clean and works on regular CDs and DVDs. The CD I tagged played perfectly in my car stereo. LabelTag isn't limited to just text either, there was an import image option although I didn't get a chance to try it.
The only thing about discs that have been LabelTagged is that you can't simply copy them anymore. You would have to rip the data off the disc and then create a new compilation.
In short, LabelTag is a cheaper and much much cooler way to label my discs.