Nero backitup can struggle when making a copy of the operating system drive (normally C:) as it is a windows program, and some file are sometime left open because you are using windows, and these do not get properly backed up. It seems to vary from PC to PC though.
Ghost on the other hand is essentially a DOS type application, and windows is not opened, and the full operating system disk can be properly backed up. Even if you use the windows interface for Ghost, it is quite clever as it sets up a virtual DOS partition, and boots to that.
I have used Ghost several times to restore the C drive with 100% success.
For the small sum of money for Ghost, it is well worth it for reliability. There are other more sophisticated back up utilities that support incremental backup etc (I think even the latest Ghost may support this), but for most home users, such features are rarely required. Most people just want to restore the disk to a known condition.