It is also available to those on CPP

Microsoft will also let those users who have Windows Vista RC1 (which means that they are on Customer Preview Program, CPP) to download RC2 as well.  Those who are interested can visit this page.  The download will be for a limited period only.  Microsoft also states that RC2 will not receive as much support as RC1 via Windows Update and that RC2 might not be able to upgrade to the full RTM version when Windows Vista ships.