As already mentioned, tool changes can be hard to justify. However, despite the hiccup in the migration, CVS to Subversion required little effort and led to almost no downtime. Perhaps the stated reasons for change didn't seem that compelling—if we'd lived without atomic commits and version controlled file systems for so long, surely we didn't really need them? The paradox here is that you can't really appreciate how important these features are until you actually use them—and so, from the other side of the change, we wonder how we ever did without them!

What I like most about Subversion though is that, from both a user's and an administrator's perspective, it's simpler than CVS. All too often a software upgrade means buying in to more features and more complexity. Think of all those new people joining the team, some of whom may never have used source control. Consider explaining the Subversion model for repository revisions, branches, tags. Now consider explaining the same topics using the CVS model. Clearly less time will be needed getting people up to speed.