Never has done for me over numerous years.
Avoid installing InCD & DragToDisk together. In fact avoid InCD totally. DragToDisk is much better if you need that feature.
I've stuck to Nero 6 & Roxio 7.5. I feel that Nero 7 is too buggy to install & in truth I don't need any of the new features & with Roxio 8 they've changed far to much to Sonic's way of doing things and nothing there to persuade me to update.
Like you I use various features of each, for instance I always use Creator Classic for mp3 & Audio CD compiling & burning but use Nero for DVD burning & data CD/DVD creation.