Add a few sentences about updating. Some older text on this subject

went away around the time of 5.0, when doing binary upgrades from
within sysinstall (at least from 4.X) was deemed hazardous due to the
huge differences between these two major versions.

It's much less risky now, and it's also high time that we mentioned
freebsd-update(8) too.

release/doc/en_US.ISO8859-1/relnotes/article.sgml

@@ -2343,7 +2343,25 @@ mdconfig_md1="-t vnode -f /var/foo.img"</programlisting>
 <sect1 id="upgrade">
   <title>Upgrading from previous releases of &os;</title>
 
-  <para></para>
+  <para>[&arch.i386;, &arch.amd64;] Beginning with &os; 6.2-RELEASE,
+    binary upgrades between RELEASE versions (and snapshots of the
+    various security branches) are supported using the
+    &man.freebsd-update.8; utility.  The binary upgrade procedure will
+    update unmodified userland utilities, as well as unmodified GENERIC or
+    SMP kernels distributed as a part of an official &os; release.
+    The &man.freebsd-update.8; utility requires that the host being
+    upgraded have Internet connectivity.</para>
+
+  <para>An older form of binary upgrade is supported through the
+    <command>Upgrade</command> option from the main &man.sysinstall.8;
+    menu on CDROM distribution media.  This type of binary upgrade
+    may be useful on non-&arch.i386;, non-&arch.amd64; machines
+    or on systems with no Internet connectivity.</para>
+
+  <para>Source-based upgrades (those based on recompiling the &os;
+    base system from source code) from previous versions are
+    supported, according to the instructions in
+    <filename>/usr/src/UPDATING</filename>.</para>
 
   <important>
     <para>Upgrading &os; should, of course, only be attempted after