I've noticed that in Windows Server 2003, you can disable NTBackup's use of Microsoft Volume Shadow Copy Service (VSS). What are the ramifications of choosing this option?

Before Windows 2003, it was impossible to back up open files, regardless of how the file was opened. Third-party software partially solved the problem but slowed the backup process and required a software purchase. VSS lets you back up open files. Consequently, you can back up open databases, email messages, and so forth without first closing the file. I certainly wouldn't disable VSS.