1- You can wait till it goes on sale. I bought nero 6 with a $50 rebate, for the retail boxed version, final cost after shipping was $27.
2- Yes, I'd say its worth it. My burn quality only increases as the software is improved. This last update has definitly improved my TY02 burn quality. Personally I have never had any OS issues, I'm running XP. Fully uninstalling Roxio may require editing the registry, unless roxio has improved its uninstaller.
3- No comment