> MacBSD-- with a new kernel, you recompile all the binaries using that
> kernal and create these snapshots, essentially a whole new release.

Not quite, unless you want to upgrade everything to current sources.
One difference from Linux is that there is one consistent set of sources
for everything--kernel, userland, etc.

There are a handful of programs that might not work with an upgraded
kernel (some of the nfs programs fit in this category, and anything that
grovels through the kernel for things and relies on the kernel and the
user program having the same view of data structures--like w, ps, netstat,
etc.  A common denominator is that all of these programs use libkvm).
Everything else should be fine using old binaries on a new system.

-allen

-- 
              Allen Briggs - end killing - briggs@macbsd.com