The MS analogy is far from apt. FreeBSD 4.5 is every bit as fast as 3.2 (if
not faster), and has many improvements and bug fixes. If you're already
using -stable then stick with it.
Unless you're really gung ho about giving yourself historical background
into the inner workings of FreeBSD, just use a recent version. If do want
to have a stab at 3.x, use 3.5.1 (ideally upgraded to the latest security
patchset version). 2.2.8 is an even earlier milestone version.
The main reason people are still using older versions can be summed up as
"if it ain't broke, don't fix it." Think about production servers and
people who administer them. Upgrading or reinstalling an OS involves some
downtime, even if it's just a few minutes. And some people just don't have
the time to do upgrades unless there's a very compelling reason. From the
standpoint of learning about FreeBSD, though, you certainly want to track
regular releases or even -stable at more frequent intervals. The only
reason I can think of you'd do a new install of an old version of FreeBSD is
to get old hardware support--MFM/EDSI disks, for example, or a NIC that uses
the le or ie driver. (MFM controller support was officially removed in 4.0.
The le and ie drivers are currently broken in 4.5 and -stable, but show some
promise of getting fixed.)
2. man chown