Information about NetBSD-current
NetBSD-current is a daily snapshot of the NetBSD development source tree. Because it is a work in progress, it may not be particularly well tested, and it may not even compile. People developing drivers and other system-level software for NetBSD are encouraged to run NetBSD-current, as are people who want to be on the bleeding edge of NetBSD development. If you're just using NetBSD for day-to-day work, you should probably be running a formal release of NetBSD instead.
The version of NetBSD-current is always in the form of N.99.M (eg: 7.99.21).
When incompatible changes to the kernel/userland-interface are made, the last component in the kernel's version number is incremented (7.99.6, 7.99.7, etc.). Hopefully, a carefully worked out upgrade path is published on the current-users mailing list. (This is why you must read this mailing list, if you are running NetBSD-current).
The developers of NetBSD have made the current development sources available to the public for several reasons. Overall, providing NetBSD-current helps us to create a more stable, accessible system.
We want it to be easy for people to become involved in the development of NetBSD. Distributing the current development sources makes it easier to get involved, because it allows a greater number of people to see where the system is going. It also makes it easier to integrate changes from users; if changes are made against the current development sources, then virtually no adjustment is needed to get those changes into the master source tree.
We also want people to test the software as we're developing it. Users of NetBSD-current are encouraged to send in bug reports about the current sources, and that helps us find and fix bugs. Because people are testing the software soon after it's written, more bugs can be found and eliminated.
People who use NetBSD-current may also want to find out the state of the bug reports. This allows a user to track the progress of a bug report they submitted or even look for bugs to fix.