CVS watch mode is on for the following reasons.
You can't accidentally modify a file, since you must run cvs edit before you can modify.
You can find out who is currently editing files by running cvs editors
If you have a particular interest in any set of resources, you can receive notification whenever any of those items are edited, unedit, or committed.
Watching is not strict locking. Five people can be editing a file at the same time, and CVS will handle those merges in the same way it always does. The watch feature just makes files read-only until you run cvs edit and lets people see everybody who is editing resources.
To release an edit, just commit your change or run cvs unedit.