The facts
Ipv4 Vs. Ipv6

IPv6 is 128 bit address represented with hex notation. It will provided 16 billion billion addresses (2 to the power of 128).
IPv6 was deployed in 1999 and will be run alongside IPv4 for many years to come.
IP subnet zero is commonly used when VLSM is implemented in network design (using the "IP subnet zero" command on a Cisco router) and Cisco would endorse this use of subnet zero, however that would obviously need to be in conjunction with a classless routing protocol such as RIPv2 or OSPF.
Check out this fast sheet on IPv6, written by ARIN.
Http://www.Arin.Net/media/fact_sheets/IPv4_IPv6.Pdf