Some basic 1.4 install questions

Being relatively new to linux and even more of a rookie on gentoo I've
got a few fundamental questions about moving up from gentoo 1.2 to
1.4-rc1.

1. Why do it at all? That is, if I begin with say gentoo 1.2 and do a
'emerge --update world' every week or so, wouldn't my software be as
up-to-date as what one would have with 1.4 (including gcc and the kernel
if I keep udating those)?

2. If I do decide to move to 1.4 should I 'update' my installation or
start from scratch?

3. Related to the previous question...if update ..how do I do it? (I
recall a 'howto' a few weeks ago that sounded complicated).

4. If new install, do folks recommend a totally clean install, i.e.,
reformatting drives, stage 1 and build it up? If so would you back up
/home, /etc, anything else?

My apologies for the newbie questions but living with gentoo is a bit
different than upgrading RH or Mandrake every 6 months!

TIA.

Terry Smith
Cape Cod USA